The Abbott government will commit a further $450 million to the fight against homegrown terrorism in Tuesday's budget as it warns of a dangerous new trend towards teenagers, some as young as 14, taking up the cause of violent extremism.

The new spending pushes the government's outlays on national security and de-radicalisation programs to well over $1 billion, despite severe budgetary pressure.

'Abbott has pointed the finger at hard-working public servants': Katy Gallagher. Credit:Alex Ellinghausen

It comes as other agencies are bracing for less money as the government struggles to meet promises of increased childcare and small business funding, while containing a budget deficit expected to be in the $46 billion range this year and almost as high next year.

But Prime Minister Tony Abbott said the threat of terrorism was not to be taken lightly.