Hardcore Brexiteers have threatened to seize upon rising regional populist sentiment and destroy the EU from within if the UK is forced to take part in European Parliament elections on May 23. Theresa May’s government has failed three times to get parliamentary approval for her EU withdrawal deal and is now preparing for the elections as she tries to agree a Brexit extension. The EU is likely to only grant a delay much longer than the June 30 date Mrs May wants - if it does at all. Earlier this week British authorities began preparing for the vote as Mrs May continue discussing the way forward with EU leaders and the opposition Labour Party. Eurosceptics, already angry the UK has failed to leave the bloc on the original departure date of March 29, claim they would be a severe impediment to the work of the EU if they have to remain part of its decision making. Mark Francois, deputy chairman of the anti-Brussels European Research Group, which he referred to as a “Spartan Phalanx,” said the EU would “live to regret it… you cannot hold a nation captive against their will”. A former armed forces minister and army reserve officer, he has a habit of using military language or referencing his father’s experience fighting in the Second World War as evidence of his indefatigable pro-Brexit spirit and refusal to give up. “If you (Brussels) attempt to hold us in the EU against the democratically expressed will of the British people, then in return we will become a Trojan Horse within the EU which will utterly derail all your attempts to pursue a more federal project,” Mr Francois told a crowd at a Bruges Group event in London. "It would therefore be much better for all our sakes if we were to pursue our separate destinies in a spirit of mutual respect," he said. The European Parliament’s proportional voting system makes it easier for candidates with fringe views to win seats, such as former UK Independence Party leader and perhaps the most prominent Brexiteer, Nigel Farage. After leaving UKIP last years over its far-right links, he has vowed to context the European elections with his new "Brexit Party". The thought of Mr Farage and his supporters striding into parliament would “hardly likely to warm the cockles of the hearts of the federalists in Brussels,” said Mr Francois. With Prime Minister Mrs May theoretically set to leave her role at some point in the future, a Eurosceptic replacement could be a huge impediment to EU decisions. In a message to the EU, Mr Francois said this new government “might well vote down your budget, veto your attempts at greater military integration and generally make it impossible for you to bring about the more federal project in which you so desperately believe in”. Another fervent Brexiteer Jacob Rees-Mogg has already said Britain “should be as difficult as possible” and block “integrationist schemes” by French president Emmanuel Macron. The latter is said to have been spooked by the comments and is trying to ensure specific conditions are put into any extension deal to stop this. There is also a fear that Eurosceptics could tap into the anger of those who just want to get on with Brexit and form alliances with the growing populist party wave spreading across the EU. Forming such a grouping could end "the dreams of many in the EU to form a much closer federal union,” said Mr Francois. It’s clear, for now, Britain’s Brexit vanguard have no intention of letting up just yet.