* DUP failed to back May on finance bill
* May's numbers in doubt on Brexit in parliament
* Northern Irish DUP: this is a message for May
* No sign of formal challenge to May's leadership
By Alistair Smout and Michael Holden
LONDON, Nov 20 (Reuters) - The Northern Irish kingmakers who prop up British Prime Minister Theresa May's government sent her a stark warning over her draft Brexit divorce deal, pulling support in several parliamentary votes on a finance bill.
The move breaches the DUP's deal with May and throws further doubt over whether she has the numbers to approve a draft Brexit deal in parliament.
Since striking a draft divorce deal with the EU a week ago, some lawmakers in her Conservative Party have tried to trigger a leadership challenge and her Northern Irish allies have said the deal threatens the unity of the United Kingdom.
May vowed to fight on and has repeatedly cautioned her critics that if they topple her, the United Kingdom will be thrust into a potentially disorderly departure from the EU on March 29 or that Brexit could be put off or cancelled.
But in an ominous sign for her Brexit deal, which must be approved by the British parliament, the Democratic Unionist Party (DUP) failed to back her minority government in several votes on a finance bill on Monday.
"We had to do something to show our displeasure," the DUP's Brexit spokesman, Sammy Wilson, said.
The votes, he said, were "designed to send a political message to the government: Look we've got an agreement with you but you've got to keep your side of the bargain otherwise we don't feel obliged to keep ours."
More than two years after the United Kingdom voted by 52-48 percent to leave the EU, it is still unclear how, on what terms or even if it will leave as planned on March 29, 2019.
The EU is due to hold a summit to discuss the draft deal on Nov. 25. Some eurosceptic ministers in May's cabinet are reported to want to rewrite parts of it, though EU governments have largely ruled this out.
British Justice Secretary David Gauke said on Tuesday talks were now moving on to Britain's future relationship with the EU.
"The withdrawal agreement is essentially done. We have had thousands of hours of negotiations with the European Commission and we have reached a deal where there have been compromises on both side," he told BBC radio.
"The withdrawal agreement meets our key objectives in terms of the integrity of the United Kingdom which is so important to all of us in government especially the prime minister."
Many business chiefs and investors fear politics could torpedo an agreement, thrusting the world's fifth largest economy into a no-deal void that they say would weaken the West, spook financial markets and silt up the arteries of trade.
May's deal is opposed by both supporters and opponents of Brexit within her party, the DUP's 10 lawmakers, the Labour Party and all other parties in parliament. She needs 320 votes out of the 650-seat parliament to get approval.
The DUP, whose political ideology is based on defence of Northern Ireland's place within the United Kingdom, say the deal divides the province from the rest of the United Kingdom.
Brexit-supporting Conservative lawmakers bluntly warned May last week that they are trying to gather the 48 letters needed to trigger a no-confidence vote in her leadership.
Thus far, though, there has been no sign that the threshold has been reached.
Since she won the top job in the turbulence that followed the 2016 Brexit referendum, May's premiership has been characterised by obduracy in the face of frequent crises.
Writing by Guy Faulconbridge; Editing by Angus MacSwan