Deputy Opposition Leader Tanya Plibersek will seek to enlist the Communications Minister, Malcolm Turnbull, in Federal Parliament as a co-sponsor to legalise gay marriage.

In a move designed to put pressure on the Coalition government over the issue, Ms Plibersek says she will introduce a private member's bill to legislate for same-sex marriage.

Deputy Opposition leader Tanya Plibersek. Credit:Andrew Meares

The move follows Thursday's High Court decision to strike down the ACT's same-sex marriage act. But crucially, Ms Plibersek says she will introduce the bill only if Prime Minister Tony Abbott allows his MPs a conscience vote.

''Mr Abbott moved to stop same-sex marriage in the ACT, and the High Court has said it's for Federal Parliament to decide,'' Ms Plibersek said.