A backlog of more than 130 nominations for heritage status at sites around Canberra — some of which have sat on the list for more than 15 years — must be addressed by the Government, the ACT Opposition says.

Opposition MLA Nicole Lawder told the Legislative Assembly the Government's Heritage Council should be given extra resourcing.

"If it's a temporary reallocation of resources that's required, then why can't we do that?" she said.

"Give them a couple of extra people for a short period of time and really pay attention to that list — make sure we are protecting things that need protection, and make sure that we're taking things off the list that don't make the cut."

Ms Lawder said there was fewer than two full-time staff members working to clear the backlog.

"It just doesn't really pass the pub test to leave something on a list for 16 years," she said.

She said many nominations on the waiting list may need to be revisited, as the rules for nominations had changed over the years.

Worries over future of Manuka shops

The lawns at Manuka shops, in October 1953. ( Supplied: ACT Heritage Library )

Local historian Nick Swain said Manuka's shopping precinct was one site that needed urgent attention.

He said a heritage nomination for the precinct's lawns and arcade had been languishing on the list for 16 years.

The precinct was built in 1924 from the designs of Walter Burley Griffin, as part of his "garden city" vision — and the suburb was named after a tea tree in New Zealand, at a time when there was hope the islands would join Australia's Federation.

This cafe in Manuka still has its original store front, which Nick Swain would like to see protected. ( ABC News: Jake Evans )

Now, only one of the original cafe facades remains and Mr Swain would like to see it protected.

The historian said some of the developments along Manuka's lawns and arcade would not have been allowed to happen if the site was heritage-listed.

"The worry is more for the future. There is nothing at the moment to stop any of this area being demolished," he said.

"If [the arcade] disappeared it would ruin the whole character of the Manuka shops."

'Annual priority list' determined by council each year

The number of items on the list for potential heritage registration peaked in 2008 at 320 nominations.

Since then, clearing the backlog has been a "highest priority", according to the Environment and Planning Directorate.

A spokesman for the directorate said the Heritage Council determined an annual priority list of nominated places and objects to be assessed at the beginning of each year.

"Issues such as whether the place or object will be affected by land release or development threats, and combining like places for comparative assessment or places that fill a thematic gap in the heritage register, are afforded a higher priority," the spokesman said.

But Mr Swain said the Kingston shops were facing development threats — and have sat on the Heritage Register waiting list for about as long as their Manuka counterparts.

"It was set up at the same time as the Manuka shops, and that heritage nomination has not been resolved either," he said.

"There is more major development around the Kingston shops that could happen very, very soon."

The directorate spokesman said the ACT Government made the decision not to place annual limits or statutory timeframes on nominations, and as such have a longer nomination list, with recent amendments to the Heritage Act.

"[This] greatly improves heritage conservation outcomes — as nominations are afforded protection under the Heritage Act," the spokesman said.