The row over MPs' tax returns rumbled on today after it emerged Jeremy Corbyn submitted his taxes using the wrong form.
It was revealed earlier this month that the Labour leader paid too much tax and filed his return late.
Mr Corbyn published a picture of his tax return to HMRC, which was filed late and declared £270 than he had earned.
The Labour leader was fined £100 for submitting the form after the deadline.
But he made a further blunder, it emerged today, because he filed a bog standard tax form, when he should have sent over a separate piece of paperwork designed for the sole use of MPs.
The form he should have filled in includes fields for declaring office expenses and benefits.
Laying out protocol for parliamentarians, the form from HMRC states: "We deal with MPs and Ministers tax records separately.
"This means that you cannot use our Online Services and must send us your completed paper tax return by 31 January 2016.
"You will need to fill in separate ‘Parliament’ pages for each office you held.
"For example, fill in one page for your post as an MP and one as a Minister in the House of Commons."
One expert, who wished to remain anonymous, said: "There's a bigger issue in that this means he hasn't filled in details of his taxable benefits, but in practice since he hardly claims any expenses I don't think this is a major issue."
When questioned on the issue, a spokesman for Mr Corbyn said: "Regardless of the form, Jeremy has published and declared all his earnings to HMRC, but we are still waiting for the Prime Minister to do the same."
