The Prime Minister has been challenged to ensure the next Strategic Defence and Security Review (SDSR) does not lead to cuts to the "conventional" military.
Dr Julian Lewis, former Chairman of the Defence Select Committee, urged Boris Johnson to recall what happened in the last combined review of defence and security, which Dr Lewis claimed was conducted "within a straitjacket of fiscal neutrality".
Speaking about the 2015 SDSR, Dr Lewis said: "It meant that every extra pound spent on cyber or security was a pound to be cut from the conventional armed forces."
Boris Johnson was asked if he could "try to ensure" the next review will "not face such a straitjacket" and will be concluded "before, rather than after, the comprehensive spending review".
The Prime Minister responded by saying he can "assure him" that it will be the "deepest review of Britain's security, defence and foreign policy since the Cold War."
"I can also assure him that, by transforming this country's economy and by raising productivity, we will ensure that defence and security are amply provided for," Mr Johnson added.
Dr Julian Lewis chaired the Defence Select Committee from July 2017 until November 2019, and was succeeded by reservist and former regular soldier, Tobias Ellwood.
Mr Ellwood told Forces News last week he would "make the case" for more funds to be made available for defence.
In September 2019, the Chancellor of the Exchequer, Savid Javid, confirmed the Government would provide £2.2 billion of funding for the Ministry of Defence over two years.
£1.2 billion of the £2.2 billion was new funding, including an extra £1 billion for 2020-2021
Delivering his Spending Review to the House of Commons, Sajid Javid said the figure represented a real-terms increase of 2.6%.