Bill Shorten congratulated the Prime Minister in Canberra over his rugby league credentials but it was a back-handed compliment.

"There's not too many people born and raised in (Sydney's) eastern suburbs who have the guts to stand up to their union mates, break out and barrack for the Roosters," the Leader of the Opposition told Malcolm Turnbull at a Parliamentary Friends of Rugby League meeting on Wednesday.

Rooster booster: Prime Minister Malcolm Turnbull with former Sydney Roosters player Anthony Minichiello.

The reference to Turnbull's "union mates" was to his rugby union supporting, top of the town, silvertail friends.

When Shorten began with, "I want to say congratulations to the Prime Minister", Turnbull interjected with, "you should make a habit of it" but surprisingly did not seize the opportunity to make a retaliatory rebuke about Shorten's "union mates", as in trade union buddies.