It comes after protesters sprayed the Ministry of Defence and Labour Party HQ in red paint over the past week.
The government is alarmed at how many people are committing criminal damage but walking free from court after claiming they had a “reasonable excuse” because they were protesting.
They are considering tabling amendments to the Criminal Justice Bill to close the loophole.
A government insider said: “Criminal damage is criminal damage.
“People who physically damage buildings have committed a criminal offence and should be prosecuted and held responsible for it.
“Ministers are considering toughening up the law to make it clear that if you commit criminal damage you should be prosecuted for it, and that protest is not a reasonable excuse.”
Earlier this week, activists linked to Just Stop Oil stormed the Labour Party head office in central London and doused it with red paint.
The protesters – known as Youth Demand – accused Labour of having “blood on their hands” over the war in Gaza.
The same group also attacked the MoD building near Parliament by spraying it with red paint.
Protesters have resorted top ever more drastic tactics over the past couple of years.
Eco zealots in groups like Just Stop Oil have frequently attacked buildings with orange paint.
Since the October 7 terror attacks on Israel, a wave of pro Palestine demos have erupted in Britain.
Activists in various anti Israel groups have targeted buildings linked to the arms trade or government.