Westminster today: Theresa May faces senior MPs questions over Cambridge Analytica and Vote Leave row - as it happened

Theresa May will use the upcoming summit of Commonwealth countries to push for action on plastic pollution in the oceans, Downing Street has said. 

The prime minister's spokesman said: 

"Marine pollution, particularly from plastics, is one of the most significant challenges facing the world today.

"And the Commonwealth, spread over six continents, is uniquely placed to take transformative action so that future generations can enjoy a natural environment that is cleaner and greener than we currently find it."

Here's our full story, by Rob Merrick, on Christopher Wiley's epic three-and-a-half-hour session giving evidence to the Digital, Culture, Media and Sport Committee: 

Theresa May is currently answering questions from senior MPs on the Liaison Committee. She starts by announcing that 25 countries have expelled now Russian diplomats in response to the Salisbury nerve agent attack, and says Russia's mission to NATO has been reduced from 30 to 20. 

Watch LIVE as Theresa May is grilled by the House of Commons Liaison Committee:

Theresa May is asked about the fact the UK spends six times more on welfare than it does on defence.

Dr Julian Lewis, who chairs the Defence Committee, says the UK meets the "bare minimum" NATO target of 2 per cent of GDP going to defence spending - a figure he suggests should rise to 3 per cent. 

Ms May replies that the UK is the second biggest defence spender in NATO and one of only six members that meets the 2 per cent condition.

She says:  "It is right that we are meeting that NATO commitment, that we remain committed to that, and that we encourage others to meet it where they don't."

Damian Collins, chair of the Digital, Culture, Media and Sport Committee, asks Theresa May if she agrees with the suggestion of Robert Mueller, the FBI special counsel who is investigating Donald Trump, that the Internet Research Agency in Moscow is being funded by the Russian state. 

Ms May refuses to answer, saying only that Mr Mueller would not made the claim unless he had evidence that it was true.

Mr Collins then asks if the Government and security services are investigating whether Russia has interfered in UK elections and referenda, including the Brexit vote. 

The Prime Minister says:

"We have not to date seen evidence of successful Russian interference in UK democratic processes"

If evidence emerges, the Government would take "robust action", she adds.

Theresa May is asked whether Mark Zuckerberg should appear in front of MPs, as they have requested. 

She refuses to answer, saying: "Mr Zuckerberg will decide for himself whether he wants to come before the committee, but what I hope is that Facebook will recognise the significance of the issue, why it is that people are so concerned about it, and ensure the committee is able to get the answers it wants"

Theresa May is asked about the plight of the Rohingya people in Bangladesh, and whether she will personally intervene to try to improve the conditions in which refugees are living in camps in Bangladesh. Ms May says Boris Johnson, the Foreign Secretary, and Penny Morduant, the International Development Secretary, have written to the Bangladeshi prime minister about the matter, and that she is also willing to intervene if need be.

A prime ministerial joke! Theresa May is asked about devolution to Wales after Brexit.

She says more powers will be devolved to Cardiff and Edinburgh after Britain leaves the EU.

The discussion then moves on to agriculture in Wales. 

Ms May says she is familiar with the issue because she often goes walking in Wales - including a trip last spring during which she famously decided to call the general election that cost her the Tories' parliamentary majority.

She says:

"I see the value of Welsh agriculture to the Welsh landscape quite often when I go walking in Wales, although given the decision I took last year, I'm not sure many would welcome my reference to walking in Wales again..."