FILE PHOTO - Dominic Raab, former Secretary of State for Exiting the European Union, leaves his home after it was announced that the Conservative Party will hold a vote of no confidence in the prime minister, London, Britain, December 12, 2018. REUTERS/Henry Nicholls

LONDON (Reuters) - Former Brexit Secretary Dominic Raab said the substance of Prime Minister Theresa May’s Brexit deal with the European Union needs to change, particularly on the issue of the Northern Irish backstop, though the means to achieve that is less important.

With just 28 days until Britain is due to leave the EU on March 29, May is still seeking changes to her Brexit deal in order to win the backing of parliament.

“The reality is the substance, rather than the vehicle or the means or the label, is what matters and we need to see substantial, substantive, legally binding changes to the withdrawal agreement,” Raab told BBC radio on Friday.

“The most obvious specific change is the ability to exit the backstop” he said, referring to an insurance policy which aims to avoid the return of a physical border on the island of Ireland.