Video: PM demands Illsley's head as disgraced Barnsley MP admits expenses fiddling

Prime Minister David Cameron and Labour leader Ed Miliband both demanded the member for Barnsley Central go voluntarily after it emerged he could keep his job and salary even if a jail term is imposed.

Illsley became the first sitting member convicted for abusing expenses when he changed his pleas to guilty at the start of his trial.

He had previously denied dishonestly claiming a total of more than 25,000, arguing that lax Commons allowances were designed to "supplement" the income of politicians.

But his barrister William Coker QC said his client admitted wrongly obtaining a revised sum of about 14,500.

The claims were made for council tax, telephone usage, service charges and maintenance, and insurance and repairs at his second home in Renfrew Road, Kennington, south London.

In a five-minute hearing, the disgraced MP, who has already been suspended by the Labour Party, sat in the dock rubbing his face and frowning.

He spoke only to confirm his pleas, saying "guilty" to the three charges of false accounting relating to three years of expenses on his second home in London.

Prosecutor Peter Wright QC said the Crown accepted the revised figure for the dishonest claims.

The judge adjourned the hearing for four weeks for a pre-sentence report.

Illsley left court alone and refused to answer questions from journalists. But Simon Clements, head of the Crown Prosecution Service Special Crime Division, said: "This was a significant sum of money and the grossly inflated claims he submitted could not be attributed to an oversight or accounting error - indeed he claimed that the expenses system was a way of supplementing members' salaries.

"By his guilty pleas he has accepted that he was dishonest in making these claims.

"As an elected representative, Eric Illsley took advantage of the trust placed in him by his constituents to act honourably on their behalf.

"Instead, he siphoned off public money into his own pockets and betrayed those who rightly expected the highest standards of integrity from him as a Member of Parliament."

The Representation of the People Act 1981 disqualifies MPs if they receive a custodial sentence of 12 months or more. In those circumstances, their seat is automatically vacated and a by-election held.

However, there is no set mechanism for expelling members who are handed shorter jail terms.

The Commons authorities indicated that the whole House would need to pass a resolution removing him from his seat. Tory Peter Baker is believed to be the last MP expelled in 1954, after he was convicted of fraud.

The Prime Minister's spokesman said Mr Cameron's personal view was that it would be "untenable" for Illsley to continue in Parliament.

"If someone has defrauded the people they are there to represent that is quite an untenable position," the spokesman said.

Mr Miliband said his former MP could no longer be a "credible voice" for his constituents.

"Eric Illsley has been found guilty of a very serious charge. He is no longer a Labour MP and I think he should now do the right thing and resign as an MP," he said.

"I do not think he can be a credible voice for his constituents having pleaded guilty to such a serious offence."

A senior party source added: "If he does not resign we will work with others to remove him from Parliament."

On Friday, former Labour MP David Chaytor - who stood down at the general election - became the first person to be jailed over the expenses scandal.

He was sentenced to 18 months after admitting he forged tenancy documents and invoices to falsely claim more than 22,000 of taxpayers' money from House of Commons authorities for rent and IT work.

Campaign group the Sunlight Centre launched an online petition calling on Illsley to quit immediately.

TaxPayers' Alliance director Matthew Sinclair said: "Taxpayers will be glad to see that justice is finally being done. But they will be outraged that any MP was able to dishonestly claim tens of thousands of pounds of their money in the first place.

"It is disgraceful that Illsley has dragged out the process and stood for Parliament again, despite knowing that he was a guilty criminal who had ripped off the taxpayers whose interests he was supposed to serve."

He added: "Illsley should resign immediately and should never stand as an MP again because he has admitted to abusing the public's trust so flagrantly."