Treasury Minister says deal's been in place for almost 30 years
Treasury Minister David Ashford says the government's bound by the amount it pays to the UK for defence and international representation.
Figures revealed earlier this week show the Isle of Man contributes more towards similar services than the other Crown Dependencies.
Since 2015 the Island's paid a total of more than £18.5million with Jersey paying £7.5m and Guernsey £5.5m.
Mr Ashford says the Channel Islands have a different agreement so make a voluntary contribution: