Builder, 43, claims Lily Allen is his sister after her dad Keith had ‘fairground fling’ 43 years ago

A builder yesterday challenged Lily Allen’s dad to take a DNA test to see if she is his sister – and that comedian Keith is his father.

Paul Luttrell, 43, claims actor Keith was just 16 when he fathered him during a fairground fling with his older mum Barbara, then 23.

The two men bear a striking resemblance with Paul sharing Keith’s swarthy looks.

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Hellraiser Keith, 59, has admitted having six children during his colourful life and is rumoured to have at least two more.

Paul says social services records from his troubled childhood show a Keith Allan being named as his dad by his mother.

But he bitterly accuses the star of refusing to admit the truth and tricking him over a DNA test which produced a negative result.

Paul, who has five sons of his own, said: “I don’t want his money and I don’t want to upset his family or cause trouble for him.

“I just want recognition, for him to own up. It upsets me, it gives me sleepless nights.

“I’m certain he’s my dad but he won’t come out and say so and I can’t understand why.”

Twice-wed Paul grew up never knowing the identity of his father and had a difficult upbringing which included one violent stepdad being jailed.

Around 18 months ago he decided to seek the truth about the identity of his own dad.

His mother, now 66, repeatedly told him he was a man named Bob Cook but after meeting him Paul believes his denials.

In October 2011 he asked social services for his case file and at that stage knew nothing about Keith Allen.

But as he thumbed through the photocopied pages – parts of them blacked out to protect other relatives – Allen’s name emerged.

In a note dated 29/10/74 – five years after his birth – a social worker wrote ‘Mrs. B (ie Paul’s mum) says Paul’s father Keith Allan….’

Another entry for the following month referring to the parentage of Paul and his sister Sophia said ‘Mrs. Brading (Paul’s mum) told me neither child is Mr. Brading’s.

“Paul’s father is Keith Allan.”

Paul Googled ‘Keith Allan’ and found photos of the actor, who had never seen before.

He said: “There was an instinctive recognition there – I immediately thought ‘I know him’.

“I showed my wife and she said ‘My God – you look so much like him’ and that’s when I started digging.”

Paul, of Bristol, researched as much as possible about Keith and read his autobiography.

He found he links with a shop in Stroud, Glos. and rang the owner, outlined the details of his social services file and asked to get in touch with Keith.

When he heard nothing back he phoned the shop again and was told ‘Keith says ‘You’re a liar, the social reports are false’.”

Undeterred, Paul decided his only option was to meet Keith in person and found he was appearing onstage in Llangollen, mid-Wales last summer.

He was stunned when fans outside started mistaking him for Keith and asking for his photo and autograph.

Paul wrote a note to Keith asking to meet him and was taken to a small room during the interval with just one other woman present.

He said: “I told him I thought he was my dad and he said ‘How can I deny it?’

“When I told him about my mum there was a blank reaction and then he said to me ‘You look worried – come here’.

“He gave me a tight hug – I thought there was some real emotion there – but as he did he said ‘You aren’t getting any money’.

“I made it clear to him I wasn’t interested in that and he said ‘Where do we go from here?’

“I said ‘I want to test it, to prove it 100% and he said ‘Ok, whatever it takes’.”

The two men swapped email addresses and in September agreed to meet at a golf course outside Bristol to carry out a DNA test using a kit Paul found online.

Paul did his own mouth swab and handed Keith the tester part of the kit meant for him.

He recalled: “He did his sample in front of me, but instead of handing it back to me to send off he took it away with mine.

“I was expecting to send them off together, but he took everything away.”

After hearing nothing for two or three weeks Paul rang the DNA testing company who said the samples had not arrived.

He emailed Keith who told him he’d left them to be posted with a member of staff at Grouchos, his favourite London club.

Two days later the lab called Paul to say the samples had arrived and had tested negative.

Keith emailed him: “I hope you are not too disappointed, it must be a big let down.

“I wish you luck in your efforts to find your biological father – maybe you should question your mother…she might have to consider some of the other possibilities.”

But Paul replied: “I have spoken to my mother and she insists she slept with two young men around that time – yourself and another guy who lives nearby and I look nothing like him.

“If I did not look like you and the time line was way off then maybe I could believe the results.

“I think it would be best if we do the test with a lawyer, doctor or authorised person.

“After 43 years do you think I will give up as I owe it to the small me at least.”

In his final email on November 2 Keith wrote: “I’m afraid I wouldn’t be prepared to undergo another test as I feel the test was conclusive….good luck…..k”

Earlier this month Lily, 27, gave birth to her second child, daughter Marnie Rose Cooper.

Paul said: “I’m convinced that Lily Allen is my half-sister, but I don’t want to cash in on her fame or upset her or her family.

“I’m pretty sure he’s kept me quiet from the rest of his family all these years because I had such a troubled background and childhood and it was easier to forget me.”

Keith Allen said: “I don’t have anything to say or comment about the matter.

“As far as i’m concerned this has been dealt with and it has been proved conclusively that I am not this gentleman’s father.”