The public expenditure minister says trade unions who don't sign up to the new public sector pay deal won't be entitled to share the benefits when it kicks in next July.

Brendan Howlin says unions who rejected the Lansdowne Road pay deal can't expect to share in its benefits when it comes into effect.

This afternoon the minister has signed official paperwork to commence the so-called 'FEMPI' [FEM-pee] laws from January, including a cut in the public sector pension levy.

But Minister Howlin says once the old Haddington Road deal expires in July, the unions who haven't signed up will be left out in the cold: