Jeremy Corbyn has suggested that all politicians and political journalists should publish their tax returns to increase transparency in politics.

The Labour leader’s comments represent a significant toughening up of the party’s line in the row over tax transparency.

Speaking on the Andrew Marr Show this morning, Corbyn said that politics should move in the direction of total openness around MPs’ earnings “so everybody knows what influences are at play”.

The tougher stance on the issue comes after David Cameron was forced into the unprecedented position of publishing his own returns, following the Panama Papers scandal. Cameron’s response to the leak, plus his handling of the ongoing UK steel crisis and the Tory infighting over the EU, has seen his personal ratings dip below Corbyn’s for the first time.

Corbyn said that Cameron still has questions to answer about his financial interests prior to becoming Prime Minister in 2010.

“Day by day a little bit more comes out about the Prime Minister’s tax arrangements, but I still think we need to know what benefit he or his trust received before 2010, why the money was put in an overseas tax haven in the first place – and if there is any tax owed on that period, then of course it must be paid,” he said.

He suggested that it was important that people serving in public office were more transparent about their interests.

“There has to be trust in people in public office. You have to know what they are earning, where it comes from and what influences come as a result of that,” Corbyn said.

“So if, for example you have a lot of money in an overseas trust and that isn’t revealed to the public then if you start lobbying not to open up the accounts of overseas trusts then it begins to look more than a little odd. So I think we have to have an openness in the transparency about it.”

Asked by Marr whether political journalists as well as politicians should publish their tax returns, Corbyn said:

“I think it’s probably a good thing if we move generally in that direction so everybody knows what influences are at play. Money and politics have to be treated with the greatest sense of openness possible so you know what influences are at work on any individual on whatever political or any other decisions they make.”

Corbyn said that as part of the current debate about money and politics, journalists should also be more open about their financial arrangements.

He told Andrew Marr: “I think we need to consider how far it goes, how far it goes to other people involved in public life. I mean, you are involved in public life for example as a very important commentator on the BBC, as indeed many others are. I think we need to know what influences at work on them are.”