The Conservatives are right to take credit for an EU policy to protect customers from hidden credit card charges, the party’s chair has said, after widespread mockery of a promotional tweet from Theresa May’s account.

Surcharges imposed by retailers, airlines and ticketing companies for using credit cards which can be as high as 20%, will be banned after an EU–wide directive.

Lewis told the BBC’s Andrew Marr Show there was nothing wrong with the Conservatives promoting the decision while the UK remained a member of the bloc.

“We are fully represented and part of that process of making those decisions,” Lewis told Marr, saying Conservative MEPs had backed the measure. “We’ve got to spread that message much more widely about the things we are doing.”

May’s official Twitter account tweeted that “we’ve banned credit card charges” on the day the new regulations were introduced, without mention of the EU.

Theresa May (@theresa_may) From today we're banning hidden charges for paying with your credit or debit card - a move that will help millions of people avoid rip-off fees when spending their hard-earned money. pic.twitter.com/EEk5jxdk7R

Guy Verhofstadt, the Brexit representative for the EU parliament, tweeted it was “refreshing to see so many embracing the benefits of EU legislation”, while the Liberal Democrat leader, Vince Cable, said the Tories were “claiming a popular policy that they had nothing to do with”.

The Labour MEP Clare Moody replied to May’s tweet saying: “No, you haven’t. This is an EU initiative from which all EU citizens will enjoy, not instigated by UK government.”

The ban on charges is among 2,557 new EU regulations and changes made since the UK voted to leave the EU in 2016, according to new data released by the House of Commons library.

The research, which was requested by the pro-EU campaign Best for Britain, found that 1,602 new EU regulations had been introduced since 24 June 2016, though they may not all be applicable to the UK.

Lord Malloch-Brown, who chairs the group, said: “These regulations show, clearly, how intertwined we are with Europe. These rules are not the Brussels diktats that the few on the extreme right pretend they are. They are rules to protect us from rogue practices and dodgy businesses.

“I guess Brandon Lewis thinks ‘we’ is also MEPs, EU commission and 26 other governments. It’s just shameless and shows how the Tories try to use Europe for their own ends.”

Lewis, the former immigration minister who replaced Patrick McLoughlin as party chair, has been charged with re-engaging with the party’s dwindling membership and refortifying the party’s online war against Labour.

Over the weekend, Lewis said the party would distribute a “toolkit” of videos and gifs for party activists to use online but told the Sunday Telegraph he was conscious that many Conservative supporters felt uncomfortable engaging in the debate online.

“What I want to see out there is more and more of our activists and people who support some of the principles we’re outlining, whether it’s a particular policy or a whole package of government reforms, getting out there in the digital world saying so and spreading that message with us,” he told the newspaper.

Lewis also said he wanted the standards of debate online to be raised, pledging Tory candidates would sign up to a code of conduct, saying Labour should do too.

“If people, our candidates, in the elections this year breach that code and there is evidence they’ve breached that responsibility pledge, we will suspend them,” he said.

“We’ve got to make sure that all of us at the very top of the party avoid this rot that we’re seeing at the top of the Labour party and we actually show, from the very top, we’ll argue our case robustly, but with respect.”