Mr Johnson has pledged to increase the police service to more than 140,000 officers by mid 2022 if he wins the race to become the next Prime Minister.
Police officer numbers in England and Wales have dropped by more than 20,000 since 2009 with Home Office figures showing a reduction from 144,353 to 122,395 in 2018.
The former Cabinet minister said the £1.1 billion move, a similar pledge to that made by former candidate Sajid Javid, would have a particular focus on rural areas that have seen the biggest reductions in police funding in recent years.
But, West Yorkshire Police and Crime Commissioner Mark Burns Williamson says he is sceptical of the comments Mr Johnson has made.
He said: "Whilst I welcome his comment, I am sceptical of the actual delivery of it.
"We have had a government that has not prioritised policing for the last few years.
"This is saying it was a mistake to cut to the number of police officers from all the forces over the last five years. Myself and many others have been been saying this for years. Here we are where there is an admittance that they need to reinvest and build up our police service."
An additional 264 police officers and staff will be recruited by the West Yorkshire force by the end of March next year, but Mr Burns Williamson said the funding has had to come from the taxpayer.
He said: "I have had to raise an additional £24 on the precept to pay for these officers because we are having to meet the demands that are continuing to rise."
Mr Johnson said the funds would come from the £26 billion "headroom" reserves set aside by Chancellor Philip Hammond.
The ex-mayor of London, who visited the Thames Valley Police training centre near Reading, Berkshire, on Wednesday, said: "What we are saying is that we are going to use some of the existing headroom, quite a small amount, about £1.1 billion, to put more police officers out on the street and I think that is what the public want."
Pressed on whether he had already pledged the headroom funds for other initiatives, Mr Johnson said: "On the contrary, we have been positively frugal by comparison with a certain other campaign that I could mention.
"We are still well within the £26 billion that the Chancellor squirrelled away quite prudently, the money is going on education, a little bit on broadband - and that is already allocated - and on policing as well."