Jeremy Corbyn was facing claims he may have failed to declare income on his tax return last night after it appeared to show that he did not take a salary as Labour leader.
Around £40,000 was missing from his official declaration to HM Revenue and Customs and aides were unable to explain the omission.
Hours after Philip Hammond refused to publish his tax return Mr Corbyn published his documents for 2015/16 in a bid to put pressure on the Chancellor to change his mind.
But he declared £77,000 in salary and allowances and £36,000 in pensions income when he should have earned around £150,000 including his pay for being leader of the party.
The six page document also stated his National Insurance and Taxpayer reference numbers.
It is illegal not to properly declare all taxable income, according to HMRC.
Last year Mr Corbyn failed to declare his three pension incomes properly and faced criticism for sending the document to HMRC late, incurring an £100 fine.
The party leader has a state pension, union income and a pension from his time in local government.
This year he employed an accountant to complete the form which stated that the party leader made £114,342 overall and paid £35,298 in tax.
Over £77,000 came from his salary as an MP, made up of £73,284 in basic pay and £3,759.96 from a London allowance to account for extra expenses incurred by MPs living in the city.
He made £1,200 in self-employed income from lectures which were declared to Parliament.
Mr Corbyn made just £78 in interest from his savings last year, the tax return revealed.
He also donated to three charities, Oxfam, War on Want and Freedom from Torture. Writing on his constituency website he said: "I am publishing the detail of my tax return here, on my constituency website.
"I have made it clear that I think it is right for party leaders to be open and transparent about their tax arrangements."
But there was confusion last night about the missing £40,000 payment he was due for seven months as Labour leader in the 2015/16 tax year.
Mr Corbyn received the top-up income as Labour leader, paid by the Cabinet Office.
In total this would amount to £69,000 for a full year but as he was only in post for seven months he would have drawn around £40,000 instead. This was not declared on the form.
A spokeswoman said the Cabinet Office does not comment on salary payments, while a Labour spokesman could not explain the missing money but told The Telegraph that Mr Corbyn's P60 form, which details income for the year, also declared £77,000.
They added: "The tax return was prepared by a team of accountants who were given all the relevant information."
The response raised questions about whether the income may have been missed off the forms or improperly declared, affecting Mr Corbyn's overall tax bill.
Mr Corbyn has never stated that he does not draw the additional salary owed to him as leader of the party.
Ahead of the Budget this week Labour vowed to force individuals earning over £1million to publish their tax return in a bid to encourage people to pay all the taxes they owe to the exchequer.
But Mr Hammond warned that doing so would put off investment in the UK.
The Chancellor refused to publish his tax return despite his predecessor George Osborne publishing his last year.
Mr Hammond told the Andrew Marr Show: “I have no intention of doing so. Just for the record by tax affairs are all perfectly regular and up to date.”