Keith Vaz has denied benefiting from his support for 42-day detention, just over an hour after David Cameron brought up the subject in prime minister's questions.
The chair of the home affairs committee is said to have received a handwritten note from chief whip Geoff Hoon the day after the vote reading: "Dear Keith.Just a quick note to thank you for all your help during the period leading up to last Wednesday's vote. I wanted you to know how much I appreciated all your help."
"I trust that it will be appropriately rewarded!...With thanks and best wishes, Geoff."
The note, which has been seen by the Daily Telegraph, was taken by the Conservatives to imply
Mr Vaz was offered deals in exchange for his support.
Journalists have been asking questions about what convinced Mr Vaz, previously a diehard opponent of plans to extend pre-charge detention of terrorist suspects to 42-days, to vote for the government.
Mr Vaz was asked in parliament whether he had been promised an honour for his support to which he replied: "No, it was certainly not offered - but I do not know; there is still time."
Mr Cameron took a strong stance on the letter at today's PMQs, hinting strongly that the prime minister was not being "straight" with people when he said no deals were made to secure the vote.