It is usually the proviso of Christmas Day snacking or visits to your nan’s. But in New Zealand – a country with a penchant for on-the-fly problem-solving – the humble biscuit tin has become a mainstay of parliamentary democracy.

There, as in Britain, members’ bills are a chance for MPs to have laws that they have proposed debated in the house.

But unlike in Westminster, in Wellington those bills are represented by plastic bingo counters in a 30-year-old biscuit tin. A curled, yellowing paper label taped to the front helpfully proclaims: Members’ Bills.

Each plastic counter represents a bill, and when there is space on parliament’s order paper for a fresh round of proposed laws, a member of the parliamentary service digs into the tin for a lucky dip.

“It was what was available at the time,” Trevor Mallard, the Speaker of New Zealand’s parliament said of the tin, adding that it had initially contained “a mixed selection of biscuits”.

The tin was introduced after parliamentary reforms in the 1980s that changed an earlier method for keeping track of members’ bills – a list – to a ballot draw.

It was just a convenient thing to use Trevor Mallard

“This was a method of randomising and keeping the ability for relatively current issues to have their chance of being selected,” Mallard said. The list, he said, had been inefficient; most bills on it were never reached.

“I think 30 years ago, random number-generating computers were probably a bit rarer than they are now, and it was just a convenient thing to use,” he said.

The tin came to international prominence this week when the team behind the BBC TV show QI tweeted about it.

“Finally! Our sophisticated randomisation apparatus gets the international recognition it deserves,” tweeted the official New Zealand Parliament account.

Finally! Our sophisticated randomisation apparatus gets the international recognition it deserves. #QIElves #nzpol https://t.co/QkdLWomBND — NZ Parliament (@NZParliament) December 16, 2019

The official receptacle is stored in an office at New Zealand’s parliament, Mallard said. “It’s not in a place where it has enormous public access but it’s not in a safe or anything.”

New Zealand is known for its socially progressive legislation, often passing bills on hotly contested issues ahead of other western countries. Some of those matters had become law only after their random selection from the biscuit tin, Mallard said.

Among them were marriage equality, legalised in 2013, and assisted dying, which will go to New Zealanders for a referendum in 2020.

“Governments often have a reluctance to lead on social change but often there are members who are prepared to stick their necks out and do what they think is right in this sort of area,” Mallard said. “This probably provides just a bit more opportunity for them to do it.”

While the tin looks a little worse for wear, Mallard does not anticipate needing to replace it.

“This was designed to keep biscuits fresh and I can’t see the … counters going off in the next hundred years,” he said.