Labour called for a criminal inquiry into the expenses of Conservative Party co-chairman Baroness Warsi as the Prime Minister acknowledged she had questions to answer.
The Opposition sought to maintain pressure on the cabinet minister by requesting police examine whether she claimed for accommodation while staying at a friend's house rent free.
MP Karl Turner wrote to City of London Police about the case - which Baroness Warsi has already asked Lords Commissioner for Standards Paul Kernaghan to investigate.
The move came amid a slew of fresh newspaper allegations against the under-fire politician, including an alleged failure to declare business interests and questions over foreign visits.
She issued a fresh denial of wrongdoing, insisting that she had acted within the rules at all times - but Mr Cameron said he accepted she needed to provide answers.
"I am satisfied that there are questions that have been raised and there are questions which have to be answered," the Tory leader said when asked about his colleague at a Number 10 Jubilee party.
"I am satisfied that will happen."
Lady Warsi says she made an "appropriate payment" to her friend - Tory official Naweed Khan, who is now one of her aides - for the nights she stayed at the property in Acton, west London.
But the property's owner, GP and former Conservative donor Wafik Moustafa, denies receiving any income from either Lady Warsi or Mr Khan during the time of her stay in 2008.
At the time, she was claiming Lords subsistence of £165.50 a night.
In his letter to the police, Mr Turner wrote: "It appears that Baroness Warsi may have claimed for expenses which she did not in fact incur, and that a criminal offence may therefore have been committed. I am writing to ask that an inquiry be undertaken into whether Baroness Warsi or her aide Naweed Khan have broken the law."
There were a number of further claims against the peer in Sunday newspapers related to her expenses, business interests and foreign visits.
The Sunday Telegraph said she failed to declare a controlling stake in a spice manufacturing firm with the House of Lords authorities.
The newspaper said February accounts for Rupert's Recipes showed Baroness Warsi held 60% of its shares - sufficient to require a public declaration.
Tory sources suggested the shares were transferred into her name for a short period only and were then passed into the hands of her husband.
Baroness Warsi said her shareholdings and directorships "have at all material times been disclosed" to all the relevant authorities.
The Sunday Telegraph also reported that she was accompanied on an official ministerial trip to Pakistan by business partner Abid Hussain - in a move compared by Labour to the Liam Fox/Adam Werritty controversy.
Dr Fox quit as Defence Secretary after his relations with the lobbyist were found to be in breach of the ministerial code.
Shadow cabinet office minister Michael Dugher has written to Cabinet Secretary Sir Jeremy Heywood asking him to investigate the various claims "as a matter of urgency".
He also raised questions about a report that the peer also made two trips to Saudi Arabia - one while a minister - at the Saudi government's expense.
"Why was it deemed appropriate for a foreign government to pay for these trips?"
He raised questions as well about the number of overseas engagements undertaken by Baroness Warsi - which the Sunday Mirror said totalled 14 over two years, costing the taxpayer £14,000.
"Given that the Minister has no government responsibilities whatsoever and that she is primarily co-chairman of the Conservative Party, why has she been allowed to go on so many foreign visits at considerable cost to the taxpayer?" Mr Dugher wrote.
Baroness Warsi said: "Neither I nor the Conservative Party nor the Government has ever met the costs of foreign visits by Abid Hussain."