Daniel Hannan MEP has scorned the "petulance" of the "governing elite" bringing a legal challenge to ensure MPs get a vote on when Article 50 is triggered.
Theresa May has announced previously negotiations over leaving the EU will be undertaken after triggering the article in March 2017. But a long-running argument brought by MPs is that the House of Commons should have a vote for when article 50 is triggered.
Investment manager Gina Miller is the main figure behind a legal case contesting the Prime Minister's authority to proceed without recourse to Parliament. The key argument of her case is that the principle of parliamentary sovereignty underpins the constitution and the rule of law.
The High Court is now considering whether ministers can invoke Article 50 of the Lisbon Treaty, the trigger for formal talks, without MPs passing a new law.
Hannan, the Conservative MEP for South East England, explained how Theresa May clearly has the authority to formally notify the EU without the vote.
"Parliament very clearly gave her the mandate when they voted for a referendum and to abide by the outcome," he told Julia Hartley-Brewer. "It's a bit rich to come back and try to change the rules now.
"What we're really seeing in this High Court challenge is the petulance of a governing elite so used to getting its way.
"When somebody says no, they behave like a toddler having a tantrum - they just can't accept the outcome.
"This is paradoxically preventing the kind of reasonable EU deal the vast majority of the 48% want."