A Labour parliamentary candidate at the 2005 General Election has defected to the Conservative Party.
Mr Chishti says he is inspired by Mr Cameron's leadership
Rehman Chishti was Labour's hopeful for the Sussex seat of Horsham, which was held by Tory chairman Francis Maude.
Mr Chishti, appointed as Mr Maude's adviser on diversity and ethnic minorities, says he has not been promised a winnable seat.
Mr Maude says he is delighted by the 26-year-old's defection. Mr Chishti says he is disillusioned by Labour.
"New Labour for me, sadly, has become more arrogant, complacent, not in touch with the views of society as a whole," he told BBC Radio 4's Today programme.
'Time to move'
He joined Labour in 1997/98 believing it was the way forward for an ex-state school boy from the ethnic minorities and with a working class background, he said.
"But that is certainly not the case," he said.
"Now with the Conservative Party led by David Cameron - committed to moving matters forward, putting forward a compassionate modern agenda - I think it is the right time to join the Conservative Party."
Pakistan-born Mr Chishti was a vice-chairman of Labour students in Wales and a Labour councillor in Medway, Kent.
He has been a political aide to Pakistan's ex-prime minister Benazir Bhutto, and worked for Labour MEP Peter Skinner and ex-MP Helen Clark.
Mr Chishti says since standing as a Labour candidate in 2005, the party "has become far more authoritarian", particularly with its attempts to introduce a crime of glorifying terrorism.
"Being a practising barrister myself, I don't even know what that means, actually," he said.
Rather than becoming a "maverick" within the Labour Party he had "decided to move on".
Pressed about whether he had been offered a winnable seat by the Tories, he retorted: "Certainly not. There's no such thing as being offered a winnable seat."
Mr Maude said: "Rehman is an extremely able and respected politician, as I found out at first hand when he stood against me.
"I am delighted that someone with his energy and talent has joined the Conservative Party. I have appointed him as my adviser on diversity and ethnic minorities."
A spokesman for the Labour Party said: "Since 1995, the Labour Party has unveiled four sitting Tory MPs, including two former Conservative ministers and the former Tory director of communications.
"In contrast, David Cameron is parading a candidate that finished third in the safe Tory seat of Horsham."