A cross-party group of British politicians went to the US to grill tech executives from Twitter, Facebook, and Google about the apparent spread of fake news on their platforms.

There is a similar inquiry taking place in US Congress, but the British inquiry is specifically examining whether Russian groups used social media to interfere with the UK's Brexit vote in June 2016.

The grilling on Thursday will last five hours, with politicians' first questions YouTube's news and policy chiefs about Google's ethics around fake news and bias.

YouTube's policy chief said the company had found no evidence of Russian groups buying ads to influence the outcome of the Brexit vote, but agreed to a further investigation.

MPs criticised YouTube for spending an estimated 0.1% of its annual revenue on moderating content.

YouTube has said it has found no evidence of Russian groups buying ads on its platform to influence the outcome of the UK's Brexit vote in 2016.

The internal investigation was the result of a probe by the UK's election watchdog, the Electoral Commission, into whether Russia may have used online platforms to interfere with the EU referendum.

YouTube's global policy chief, Juniper Downs, said the firm would cooperate with any further British investigation into political misinformation.

"We're happy to cooperate with a UK government investigation in any interference in elections," Downs said. "We have conducted [research] around the Brexit referendum and found no evidence of interference. We looked at all ads with any connection to Russia, and there is no evidence of our services being used."

Downs made her comments during an evidence hearing with British politicians in the US on Thursday. The UK's Digital, Culture, Media, and Sports select committee is conducting its own ongoing investigation into fake news, and specifically the possible impact of Russian groups spreading misinformation around Brexit. That investigation is separate from the Electoral Commission's probe.

In an unusual move, the group of 11 politicians has travelled to the US to gather evidence in Washington and New York, as well as in London. They summoned Downs, Google's news chief Richard Gringras, plus executives from Facebook and Twitter to give evidence on Thursday.

Google's vice president of news, Richard Gringas, and YouTube's global head of policy, Juniper Downs. Parliament TV

The cross-party group spent more than an hour attacking YouTube and Google for its role in spreading fake news, contributing to the decline of journalism, and on its spending on removing abusive or misleading content.

Downs said during the grilling that YouTube had committed "tens of millions of dollars" on solving the problem of fake news, both by investing more in technology and moderators.

But MPs claimed this was a fraction of what YouTube could spend.

Committee chair Damian Collins repeatedly asked Downs how much YouTube earns annually, something Google doesn't disclose in its earnings.

After Downs claimed not to know the figure, Collins gave an estimate of $10 billion (£7.12 billion). Credit Suisse predicted YouTube's earnings would hit $6 billion (£4.2 billion) in 2015, so it's a reasonable guess.

Collins pointed out YouTube commitment to spending more tackling fake news and inappropriate content amounted to just 0.1% of its estimated annual revenue. "This is a small sticking plaster over a gaping wound," he said.

Downs responded: "I'm not sure the financials behind this are the right metric. Technology does a lot of the work at scale, to identify [content] at speed. To quantify in people hours how many hours of human endeavour are being saved by technology, we would get to a much faster number."

The five-hour hearing will continue with Facebook and Twitter.