SNP politicians whose alternative proposals for independence will not be debated at party conference have called on the leadership to set out plans for leaving the UK if the new prime minister blocks a further referendum.

SNP MP Angus MacNeil and the party's group leader on Inverclyde Council, Christopher McEleny, wanted their plan to be debated at the SNP conference in October where it could have become official party policy.

It calls for a vote on independence to take place by autumn 2020, and states that if the UK Government fails to grant a Section 30 order to enable this to happen, voters returning a majority of independence-supporting MSPs or Scottish MPs would give a mandate to the Scottish Government to start independence negotiations.

The proposers believe this could have provided a way around the next prime minister refusing to grant permission for a second independence referendum, as both Conservative leadership candidates oppose a further vote.

However, the resolution for debate has not been selected as part of the provisional agenda for the SNP autumn conference.

In a joint statement, MacNeil and McEleny said: "We are disappointed that it has been deemed that debating a credible plan on how to progress the case for actually delivering independence isn't worthy of the agenda at SNP conference.

"When the Scottish Government request a Section 30 order we know the answer is going to be 'No'.

"Our plan, set out a means of ensuring Scotland's voice was heard, and it progressed our mandate for a referendum as it should be deployed, with democratic determination.

"The plan received much support from across Scotland, therefore we are looking forward to the party leadership now setting out their plan B to ensure that Scotland's destiny does not depend on the mood and vagaries of the UK Government, but of the Scottish people.

"The Scottish Government now has to show leadership on this issue and conference must be given a roadmap as to how the leadership believe we will deliver independence.

"Meanwhile it surely is past time, three years after the Brexit referendum, that a focused campaign on independence is launched with Scot Gov backing – merely announcing legislation through the parliament as was done in April is not enough."

An SNP spokeswoman said: "The process of producing the provisional agenda is the internal business of the Scottish National Party, with motions shortlisted by a democratically elected internal body.

"The SNP already has a cast-iron mandate for holding an independence referendum before the 2021 election, and the First Minister has made clear that she believes this should take place in the second half of next year."