NZ First's support would come only if immigration levels were cut at the same time.
The Maori Party could not be reached for comment.
New Zealand has not increased its refugee quota for 30 years. It is ranked 87th in the world for total refugee resettlement per capita.
There are currently around 52 million refugees around the world - numbers not seen since the end of World War II.
"This is a very exceptional situation ... countries like New Zealand, which is amongst the richest countries in the world, need to take their fair share," Mr Shetty told the Herald.
"It won't change everything if the quota goes from 750 to 1500, but it all adds up. For those 750 extra people who are resettled it makes a world of difference ... they are not drops in the ocean, they are real human beings with families.
"If every country starts saying what they do doesn't make a difference, what's going to happen to the refugees in the world?"
Before meeting Mr Shetty, Mr Key reiterated that he will not relent to calls to increase New Zealand's refugee quota.
It was more important to resettle the existing quota of 750 per year rather than increase the total number of refugees, he said.
Mr Shetty's visit comes in the same week Mr Key said a boat of asylum-seekers turned back from Australia had a credible chance of making it to New Zealand.
Poorer countries were shouldering far greater refugee numbers, Mr Shetty said.
He was travelling to Lebanon in two weeks and would ask the country not to close its borders to refugees.
"They had a million people coming into the country ... how will we ask the Lebanese Prime Minister to not shut their boundaries if we can't say that New Zealand is even going to take 750 people more?"
New Zealand will hold the presidency of the UN Security Council in July, and Mr Shetty also asked Mr Key to push for the five permanent members - France, the UK, the US, Russia and China - to voluntarily drop the power of veto on human rights issues.
Foreign Minister Murray McCully has previously criticised the council's inability to act because of the veto.