The Claim: Brexit-backing Conservative MP Peter Lilley told BBC Radio 4's Today programme that every week the UK stayed in the EU would cost £250m in EU budget contributions.
Reality Check verdict: £250m is a weekly figure the OBR estimated the UK would have sent to the EU in 2019-20 had the EU referendum never taken place.
It is not a "net" figure as it does not take into account the amount the UK would receive from the EU.
How much money, if any, the UK will contribute to the EU budget at the end of Article 50 negotiations is a matter of pure speculation at this point.
Former cabinet minister and pro-Brexit MP Peter Lilley spoke against a transitional deal with the EU.
The Chancellor, Philip Hammond, suggested one would be needed once the UK completed the Article 50 negotiations to exit the EU in March 2019.
Mr Lilley said that every extra week the UK stayed in the EU would cost the UK £250m net in contributions to the EU budget.
This figure is calculated on the basis of the latest five-year economic and fiscal forecast produced by the Office for Budget Responsibility (OBR).
This matters because we are talking about projections the OBR makes on the basis of concrete government policies.
The difficulty is that when it comes to Brexit, it is not yet known what the policy positions of the UK government - or the EU - will be in the coming years.
The £250m a week figure is the OBR's estimate for the UK's transfers to the EU in that particular year had the Brexit vote never taken place.
The estimate is for 2019-20, the year in which the deadline for Article 50 negotiations will lapse if the government triggers Article 50 by the end of March 2017.
The government is committed to leaving the European Union.
The size and scope of future UK contributions to the EU budget will wholly depend on the decisions made by the UK and the EU during the forthcoming negotiations.
'Bone of contention'
The OBR has not attempted to estimate the amount of money the UK could send to the EU after Brexit.
Instead it made the "the fiscally neutral assumption" that any money the UK would save by no longer contributing to EU institutions would be "recycled into other domestic spending" in order to make up for the loss of existing EU spending in the UK, among others.
The question of how much money the UK sends to the EU each week has been a bone of contention during and after the EU referendum campaign.
As we highlighted previously, in 2014 the UK sent roughly £276m a week to the EU but received about £115m a week in return, bringing the net contribution to the EU to £161m a week.
The Treasury is expected to publish the 2015 EU budget figures later this month.