Brexit sparks showdown between UK Parliament and government

British conservative lawmaker Anna Soubry, centre, who campaigned to remain in the European Union during referendum debates, reacts with pro-Brexit pr

British conservative lawmaker Anna Soubry, centre, who campaigned to remain in the European Union during referendum debates, reacts with pro-Brexit pr

Pro-Brexit, left, and anti-Brexit, right, protesters debate their views outside parliament in London, Thursday Jan. 10, 2019. Prime Minister Theresa M

Pro-Brexit, left, and anti-Brexit, right, protesters debate their views outside parliament in London, Thursday Jan. 10, 2019. Prime Minister Theresa M

Anti-Brexit demonstrator makes his views known, outside parliament in London, Thursday Jan. 10, 2019. Prime Minister Theresa May's proposed Brexit dea

Anti-Brexit demonstrator makes his views known, outside parliament in London, Thursday Jan. 10, 2019. Prime Minister Theresa May's proposed Brexit dea

Britain's Prime Minister Theresa May reacts ashildren play rugby, during a visit with Japanese Prime Minister Shinzo Abe to Twickenham Rugby Stadium,

Britain's Prime Minister Theresa May reacts ashildren play rugby, during a visit with Japanese Prime Minister Shinzo Abe to Twickenham Rugby Stadium,

Britain's Prime Minister Theresa May speaks during Prime Minister's Questions in the House of Commons, London, Wednesday, Jan. 9, 2019.  The British g

Britain's Prime Minister Theresa May speaks during Prime Minister's Questions in the House of Commons, London, Wednesday, Jan. 9, 2019. The British g

LONDON (AP) — As Brexit enters its endgame, the big divide is not between the U.K. and the European Union, but between Britain's government and Parliament.

Since Britain struck a divorce deal with the EU late last year, the executive and legislature have been at war.

Prime Minister Theresa May is struggling to win backing for the agreement ahead of Parliament's vote next week while lawmakers try to grab control of the Brexit process.

The battle has destabilized a country without a formal written constitution and where democracy rests on centuries of law, precedent and convention.

London School of Economics Professor Iain Begg said Thursday that Britain is "getting very close" to a constitutional crisis.

He says "if Theresa May loses the vote next week, we don't actually know what happens next."