"That would be grossly unfair on good landlords, who are the vast majority in this country"

From Hansard, debate on Tenant Fees Bill, 23 January 2019:

Bob Blackman Conservative, Harrow East:

The issue for us was that four weeks [maximum deposit] would lead to a position whereby the tenant had an incentive to say, “Okay, I won’t pay the last month’s rent—just take it out of the deposit,” and then if the landlord could reasonably wish to claim money from the deposit because of damage or other reasons, they would have to pursue court action to recover it.

That would be grossly unfair on good landlords, who are the vast majority in this country.

Other members of the Committee promoted six weeks, so we ended up with the view that five weeks struck a balance between giving tenants an incentive to pay their last month’s rent, in the knowledge that they would get back their deposit had they been good tenants, and landlords being forced to go through a proper claim process to recover moneys as a result of damage by a tenant.

He's wrong in principle and wrong in logic. If a tenant has wrecked the place and plans to move out soon, then whether he's paid three, four, five or six weeks' deposit, he won't bother paying the rent any more, and he either leaves of his own accord or waits until he is evicted.

I thought that most tenants didn't bother paying the last month's rent* anyway, which makes perfect sense. They need the money for the deposit on the next place. Landlords and letting agents often wait weeks before returning a deposit to those tenants gullible enough to pay the last month's rent. If the tenants pay it, it is often very difficult for them to scrape the next deposit together, so they can't move out at all. Catch 22.

* I used to be a BTL landlord, most of them didn't bother paying the last month's rent, so I kept their four-week deposit instead, never bothered me and everybody's happy.