LONDON (AFP) - A rebellion in Britain's Parliament over Brexit legislation spells trouble ahead for Prime Minister Theresa May as she heads to an EU summit Thursday (Dec 14), hobbled by divisions within her party.

May took over after the 2016 Brexit referendum and called a general election in June, hoping to strengthen her hand in the negotiations with Europe.

However, the gamble backfired and she lost her centre-right Conservative Party's parliamentary majority, forcing her into a deal with Ulster's Democratic Unionist Party (DUP) for support.

She has since faced several humiliations at home and abroad, with the preliminary Brexit deal in Brussels last week standing out as a rare exception.

Here are the five main sources of weakness for May:

The new rebels

Eleven Conservative MPs voted against the government on Wednesday to force through an amendment that will give Parliament a binding vote on whether or not to accept any eventual Brexit deal with the EU.

The vote follows months of rumblings from pro-EU Conservative MPs who previously always backed down from a confrontation with the leadership.

The concern now is that this group could cause more trouble, including next week when they will be demanding another change in Brexit legislation to remove any mention of the date of March 29, 2019 as the day Britain leaves the EU.

"It has broken the dam," a Conservative MP was quoted by The Guardian newspaper as saying.

"It will be much, much easier to do it again. Rebelling once gives you a taste for it," the MP said.

Power of Parliament

The amendment passed on Wednesday means May's government will not be able to conclusively push through a Brexit agreement whether or not Parliament is in favour.

Parliament could now in theory force Britain's government to go back to the EU to renegotiate if it does not accept the terms of the withdrawal agreement.

In practice, it may be difficult for MPs to vote against an agreement as this could plunge Britain into a period of political and economic turmoil.

But the vote also has major symbolic implications as it gives MPs greater control of Brexit talks.

DUP pulling the strings

May's deal with Northern Ireland's DUP means that there is little she can do without the say-so of its leader Arlene Foster.

The DUP initially scuppered a Brexit deal in Brussels, telling May that they would not accept any deal that could lead to regulatory divergence between Northern Ireland and the rest of Britain.

May was forced to return to London empty-handed and hold talks with the DUP where she agreed that Britain as a whole would align itself with some EU trade laws if necessary to keep a free-flowing border between Northern Ireland and the Republic of Ireland.

Economic trouble?

The Brexit referendum led to a sharp devaluation in the value of the pound against the euro and dollar, spiking inflation and hitting the purchasing power of Britons.

Business leaders have called on the government to agree a post-Brexit transition period quickly.

Many companies, particularly in the powerful financial sector, have said they will otherwise be forced to open offices in continental Europe to ensure continuity in business operations.

Britain has slashed its forecasts for economic growth and the prediction is now an annual rate of between 1.3 per cent and 1.5 per cent over the next four years.

Cabinet divided on Brexit

May has been cagey about the type of relationship she would like Britain to have with the EU post-Brexit.

That is partly because her ministers' views are divided, ranging from a close economic partnership to a far looser arrangement that would see Britain orient its trading relationships beyond the EU.

Finance Minister Philip Hammond, seen as one of the moderates, told a parliamentary committee last week the Cabinet had only had "general discussions" about future UK-EU trade ties.

"We haven't had a specific mandating of an end state position," he told MPs.

Ministers are due to address the issue at a Cabinet meeting next Tuesday, where tensions could emerge between moderates and more pro-Brexit Cabinet members such as Foreign Secretary Boris Johnson.