Halifax MP Megan Leslie is defending her decision to vote in favour of the bill designating Sable Island, located off the coast of Nova Scotia, a national park.

Bill S-15 passed through the House of Commons late Tuesday night after almost being quashed hours earlier. It was not supported by the Green Party, but the Conservatives and the New Democratic Party voted unanimously in favour.

Green Party Leader Elizabeth May, who fiercely opposed the bill, said the legislation does not properly protect the island from all industrial development.

Leslie agrees the bill is not perfect, but she said she'll work on incorporating improvements.

"Yesterday, oil and gas companies could drill on Sable Island and today with royal assent they won’t be able to. We were in a situation last night where we knew the House was going to rise, we knew the House would adjourn. Witnesses said ‘look the most important thing here is protect this park. Make amendments to get rid of the drilling underneath, make amendments to get rid of the exploration on the surface.’ And we did," Leslie said.

May said it's wrong to allow the Canada-Nova Scotia offshore petroleum board to make decisions about development at Sable Island.

She also disagrees with Leslie about urgency. The Green Party leader had hoped to muster public support this summer and return to the bill in the fall.

Sable Island has become Canada’s 43rd national park.

Sable Island, about 300 kilometres southeast of Halifax, is 42 kilometres long. It's known as the Graveyard of the Atlantic because it's ringed by 300 years of shipwrecks.

It's home to an estimated 400 wild horses, descendants of animals brought to the island during the late 1700s. It's also the breeding ground for seals and birds, including the rare Ipswich sparrow.

Fewer than 250 people visit the island every year, but that number is expected to jump. Parks Canada is working on a management plan.