British Home Secretary Amber Rudd | Jack Taylor/Getty Images UK Cabinet at odds over delay to Brexit immigration bill Brexiteers see the bill as key to the UK’s preparations for no deal, but it has been delayed until late 2018 or early 2019.

LONDON — Members of the U.K. Cabinet are pressuring Home Secretary Amber Rudd to bring forward a key immigration bill not due before parliament until the end of the year, amid growing tensions within government over Britain's readiness for a "no-deal" scenario in the Brexit negotiations.

The bill is crucial to the U.K.'s plans to control EU immigration post Brexit, but some fear the ongoing delay means it will not be ready in time for Britain's departure from the European Union on March 29, 2019.

There is also increasing frustration within the Cabinet that the failure to bring forward the bill is undermining other key Brexit legislation that must be passed before Britain's exit from the bloc, as well as creating uncertainty for British servicemen with foreign partners or family who are waiting anxiously to see how the new regime will work.

The row, which has dragged in the Defense Secretary Gavin Williamson, reflects the ongoing divisions over Brexit within the government — exposing the scale of the challenge Theresa May still faces to unite her party on the terms of the final Brexit deal before the vote in parliament expected some time after October.

Brexiteers say that the bill is vital to the U.K.'s preparations for no deal in the Brexit talks and should not be delayed until the last minute to ensure there is enough time to prepare in case the negotiations with the EU collapse.

The bill will end freedom of movement, impose new national laws on immigration and allow the U.K. to crack down on fraudulent use of European ID cards.

There is concern among some senior members of the government that the delay is part of a wider ploy by former Remainers to undermine the viability of "no deal," forcing the prime minister to accept whatever terms are on offer from Brussels for a transition agreement which extends the deadline for passing key Brexit legislation.

Advocates of a "soft" exit from the EU insist that the delay is not a strategy to thwart preparations for "no deal" but simply a reflection of the fact that other issues take priority, including reaching an agreement on a transition period expected at the European Council in March and securing a deal on the rights of EU citizens living in the U.K.

The immigration bill is a key plank of the government’s agenda and was set out in the queen’s speech last year. The bill, which has been drafted already, will end freedom of movement, impose new national laws on immigration and allow the U.K. to crack down on fraudulent use of European ID cards.

Assuming there is a Brexit deal this year, the changes will not come into effect until the end of a post-Brexit transition period — which will finish most likely in December 2020.

According to one U.K. official familiar with the progress of the bill, Rudd was called to a meeting of the parliamentary business and legislation committee (PBL) on February 27 to provide an update on the progress of the bill. If no deal can be reached with the EU, the U.K. would crash out on March 29, 2019 without a transition period, so the new immigration system would need to be in place much earlier than expected.

The delay to the immigration bill being brought before parliament until late this year or even early 2019 — leaving a matter of just a few months to get the bill onto the statute book — is having a knock-on effect on the crucial “access to benefits bill” which had been pencilled in to be published in the spring after the EU summit later this month.

The benefits bill, which has been drafted for publication by David Gauke’s Department for Work and Pensions, will need to be rewritten if the immigration bill is not introduced at the same time. Without the immigration bill, new clauses will be needed to deal with the entitlement to benefits of EU citizens in the U.K. after Brexit, which should have been covered by the Home Office legislation.

“The point we are at now is we are expecting a note on why the Home Office does not think the bill is needed now,” said one official from the committee.

The committee expects the note to set out how the Home Office is preparing for a no deal without an immigration bill given that the U.K.'s official leaving date is now just over 21 months away. Rudd has already written to the Leader of the House Andrea Leadsom to set out her plans.

According to the official who spoke to POLITICO on condition of anonymity, Rudd wants three non-Brexit bills brought before MPs before the immigration bill.

“There has been a lot of to-ing and fro-ing about this. There are a few ministers who have concerns about it" — Senior government official

Some Brexiteer ministers are concerned that Rudd is delaying in an attempt to scupper preparations for no deal — something they regard as key to bolstering the U.K.'s negotiating position. Rudd supported Remain in the referendum.

One minister, who confirmed the delay to the immigration bill, said there was widespread frustration at the home secretary. Williamson, the defense secretary, for example, is angry at the uncertainty faced by servicemen and women whose partners are from outside the U.K. and are waiting to see what system will be put in place after Brexit, although like other EU citizens they are covered by the agreement reached with the EU on citizens' rights in December.

A senior government official said: “There has been a lot of to-ing and fro-ing about this. There are a few ministers who have concerns about it. Gavin is keen that there is clarity on this issue for servicemen and women and their families.”

Ministers believe the benefits bill may have to be changed to accommodate for the lack of an immigration bill, opening up the possibility of hostile amendments between the government and opposition — further complicating the government’s plans.

“The Home Office believes it’s too difficult so doesn’t want to bring it forward,” said one official. “But it will always be difficult. It needs to be in place in case we can’t get a deal.”

The FT reported last month that the delay to the government’s immigration bill was to allow the Home Office to take in the conclusions of the Migration Advisory Committee’s inquiry into the costs and benefits of European migrants to the U.K. economy, due to be announced in September.

A spokesperson for the Home Office said: “We are confident that our immigration systems will be ready for Brexit and have been working to develop the details of the settlement scheme for the three million EU citizens already in the U.K. — as well as the registration of new EU arrivals after March 2019.

"We will publish further details of this over the coming months, but the Government is currently focused on successfully negotiating the terms of the Implementation Period with the EU. The Immigration Bill will be introduced when Parliamentary time allows,” the spokesperson added.

This article has been updated with a response from the Home Office.