U.K. Prime Minister Theresa May admitted March 25 that her twice-defeated Brexit deal with the EU still lacks majority support to clear the House of Commons, warning that crashing out of the bloc without a withdrawal agreement remains the default path forward.

"It is with great regret that I have had to conclude that as things stand, there is still not sufficient support in the House to bring back the deal for a third meaningful vote," May told lawmakers ahead of a vote March 25 in London in which the House of Commons could take control of the Brexit process from the government.

"I continue to have discussions with colleagues across the House to build support, so that we can bring the vote forward this week and guarantee Brexit," May added.

If her deal cannot be revived for another vote, May said, the government is committed to "work across the House to find a majority on a way forward."

The EU has said the March 29 Brexit date would be delayed until May 22 if the U.K. Parliament ratifies a Brexit deal this week. But if lawmakers again fail to approve a deal, the EU would give London only until April 12 to decide on its course of action, including a no-deal Brexit. House of Commons Speaker John Bercow has said May's deal cannot be put to another vote in its current form. A bill due to be voted on this week would push the Brexit date from March 29 to April 12 to match the EU offer in the event that no withdrawal deal is reached.

Conservative MP Oliver Letwin brought forward a proposal that, if passed late March 25, would pave the way for a series of "indicative votes" March 27 on alternative Brexit options. A similar proposal was defeated in Parliament by a narrow margin earlier in March.

May said the government will oppose the new proposal. She is "skeptical" about using indicative votes, saying they could "overturn the balance of our democratic institutions."

"When we have tried this kind of thing in the past, it has produced contradictory outcomes or no outcome at all," May said, warning that the indicative votes could lead to a Brexit outcome that is not negotiable with the EU.

"So I cannot commit the government to delivering the outcome of any votes held by this House. But I do commit to engaging constructively with this process," May added.

Besides May's deal, other possible Brexit options include revoking Article 50, the legal clause under which the U.K. is set to quit the EU; a second national referendum; opting for a standard trade agreement between the two sides; May's deal including retaining membership of the EU customs union; her deal including membership of the EU's customs union and the single market; and no deal.