The chancellor, Sajid Javid, will commit an extra £2bn for no-deal Brexit planning, the Treasury has announced, taking the running total for preparations to more than £8.3bn since the 2016 referendum.

Javid is due to formally unveil the money as part of his spending round statement to MPs on Wednesday, although it remains to be seen whether this will take place as planned given moves by backbench MPs to take control of the Commons agenda.

Downing Street insisted the spending review would happen in some form. However, it is understood that if the order paper is revised to make space for the backbench bill seeking to delay Brexit, it could take place as a written statement.

The Treasury said the extra £2bn would be spent on post-Brexit projects and would include cash for the Border Force, for the Department for Transport to assist ports, and for a possible UK replacement for the EU’s Galileo satellite navigation system.

The £8.3bn running total for no deal comprises the original £4.2bn, an extra £2.1bn allocated in August for contingencies such as stockpiling medicines, an additional 500 border officials and a public awareness campaign, and the new £2bn.

In a statement before the spending round, Javid said: “One of my first acts as chancellor was to announce £2.1bn additional funding to prepare to leave the EU. We’ve now provided £8.3bn to help departments prepare for Brexit. This new funding will ensure that departments can grasp the opportunities created by Brexit after we leave on 31 October.”

In an earlier update to MPs on no-deal planning, Michael Gove, who leads on the issue for the government, said the Operation Yellowhammer dossier on no-deal risks – which has been leaked but not published – depicted a “reasonable” worst-case scenario.

“Operation Yellowhammer assumptions are not a prediction of what is likely to happen. They are not a best-case scenario or a list of probable outcomes, they are projections of what may happen in a worst-case scenario,” he said.

Gove conceded there would be issues connected to no deal, such as tariffs and checks on the Irish border. He added that while businesses and the public should not be “blithe or blase” about the challenges, the risks could be mitigated and “we can be ready”.

Jon Trickett, the shadow Cabinet Office minister, said Gove’s statement was “rather vacuous”, adding that if a general election was called he would ask the civil service to publish all documents related to no-deal preparations.