Liam Fox also agreed to publish his return but only if he makes the final two candidates, while Stephen Crabb will publish but did not confirm when. Theresa May is also expected to publish her return, possibly today.

Ms Leadsom has previously faced scrutiny over her tax affairs for using offshore bank accounts as part of a property business she ran with her husband.

The leadership hopeful set up a buy-to-let company in 2003 before investing £1 million in properties in the south of England.

Ms Leadsom later used an account at Kleinwort Benson (Channel Islands) Ltd, based in Jersey, to deal with charges before transferring shares to her two children to be held in trust.

She later transferred the offshore charges to the UK before becoming a Treasury minister and subsequently stepping down as the director of her buy-to-let business, handing it over to her son instead.

Mr Gove published his tax return, revealing that he earned £214,242 as an MP and minister over the past two years and paid £67,000 in tax.

The returns reveal that as education secretary he earned a total of £117,786 in 2013-14. However, after he was demoted to chief whip in the run up to the election his income fell to £96,456 in 2014-15.

A spokesman for Mr Gove, who is in the running to become the next Conservative leader, said: “Michael accepts that candidates for the job of prime minister should be transparent about their income and tax affairs.”

When asked yesterday, the Home Secretary, Mrs May, also promised to declare her taxes by publishing the return, however she echoed Ms Leadsom and warned it should not become the norm for all standing MPs. The details of Mrs May’s salary and tax are expected to be released later today.

Speaking to ITV’s Robert Peston, she said: “I think it’s important that politicians are judged by what they do and how they deliver for people. “And I don’t think it’s the case that all members of parliament should have their tax returns published, but if people feel that somebody who is going to be prime minister should publish their tax return, then I will do that because mine’s very simple and straightforward.”

Earlier this year the Chancellor, George Osborne, Prime Minister, David Cameron, and Labour leader, Jeremy Corbyn, all published information about their income and tax affairs.

At the time, a Downing Street spokesman said potential prime ministers should be made to publish their tax returns.

Asked on The Andrew Marr Show if she would publish her tax return in full Ms Leadsom said: “Yes, I’m perfectly happy to publish my tax returns.”

Asked whether the information would be published before the vote to decide the next Conservative leader she said: “I’ll have to think about that, but in principle I have no problem with it” before adding: “Yes, OK, yes.”