The Scottish parliament vote on calling for a new independence referendum has been postponed until Tuesday 28 March, the day before Theresa May triggers article 50 to begin the Brexit process.

MSPs were in the closing stages of a debate on Wednesday afternoon about Nicola Sturgeon’s bid to stage a second independence referendum by spring 2019 when the sitting – and a decisive vote on the proposal – was suspended after the terror attack at Westminster.

With its flags flying at half mast, Holyrood’s business bureau decided on Thursday morning not to immediately restart the debate, arguing it would be inappropriate to do so just as Westminster was resuming its daily business after the attack.

It is understood Holyrood’s five parties were split on the timing. The Scottish Tories, Labour and Lib Dems wanted to resume the debate on Thursday after first minister’s questions but the Scottish National party and Scottish Greens opposed this.

The SNP originally proposed staging it next Thursday, the day after May invokes article 50, but agreed to a Scottish Green party compromise offer to use its debate slot on Tuesday instead.

If Sturgeon wins the vote on Tuesday afternoon as expected, the first minister is highly likely to approach May in the final hours before the prime minister triggers article 50 on 29 March to ask for the legal powers to stage the referendum.

May is also due to visit Scotland before she invokes article 50 as part of her tour of the UK to promote her Brexit strategy, again heightening tensions over Scotland’s constitutional future.

Holyrood’s business bureau agreed to change the format of first minister’s questions to allow party leaders to ask about the attacks at Westminster in lieu of a formal statement, instead of the party political disputes that normally occupy that slot.

Echoing Westminster’s decision to resume its scheduled business, first minister’s questions will be followed by a Scottish government ministerial statement on childcare and a debate on British sign language at Holyrood.