Number 10 officials have declined to clarify whether the PM cycled to the park or was driven there in a vehicle.
Official Government guidance on exercise says it should be limited to once a day and “you should not travel outside your local area”.
Policing Minister Mr Malthouse was pressed on BBC breakfast whether seven-miles away was “local”.
He replied: “It depends where you are. Obviously seven miles will be local in different areas and in different times.”
He said the key thing was people to maintain social distancing, adding: “I understand that this is a sort of scotch egg moment where people are searching for the loopholes and the problems in the law.
“Unfortunately we can’t legislate for every single dynamic of human existence.”
On Sky News, Mr Malthouse also admitted that “local” was open to interpretation and said: "What we are asking people to do is when they exercise to stay local.
"Now, local is, obviously, open to interpretation, but people broadly know what local means.
"If you can get there under your own steam and you are not interacting with somebody ... then that seems perfectly reasonable to me."
It comes after the Evening Standard exclusively revealed the PM was spotted in the east London park wearing his TfL hat and a face mask alongside his security detail.
A Number 10 source added: “The Prime Minister follows Covid rules closely to try and limit the spread of the virus.”