Failure to pass the Scottish Budget would create a “thick layer of uncertainty” for businesses at an “already challenging time”, retail chiefs have warned.

With Finance Secretary Derek Mackay apparently unable to find opposition support for his draft tax and spending plans, the Scottish Retail Consortium (SRC) urged politicians to take a “collegiate approach” to ensure the proposals can pass through Holyrood on Thursday.

That marks the first opportunity for the Scottish Parliament to vote on the 2019-20 Budget.

While the six Scottish Green MSPs have backed the minority SNP administration’s budget for the last two years, co-convener Patrick Harvie claimed the “hugely damaging” proposals for the coming year would lead to massive cuts in local services.

The Budget includes an additional £730 million investment in health services north of the border and £180 million aimed at boosting attainment in schools – with £5 billion of capital investment including £1.7 billion spending on transport infrastructure and a £50 million town centre fund to support struggling high streets.

Meanwhile, tax changes outlined in the plans will increase differences between Scotland and the rest of the UK.

From April, taxpayers south of the border will only pay income tax at the 40p rate if they earn more than £50,000 a year – while in Scotland it is proposed people will pay the higher rate of 41p on earnings above £43,430.

SRC director David Lonsdale said while the plans that have been put forward are “far from perfect”, there was much in the draft Budget that retailers supported, including funding for town centres and income tax proposals aimed at “protecting ordinary workers” from higher bills.

With the UK’s departure from the European Union just two months away, he stressed the damage uncertainty could have on firms.

Mr Lonsdale said: “In the current volatile economic and political climate, businesses need as much certainty as possible. That’s why it’s crucial MSPs take a collegiate approach to ensure a Budget which supports economic growth is passed without delay.

“Robust debate and scrutiny over the coming days is both right and necessary, however any failure to pass a Budget in good time would add a thick layer of uncertainty at an already challenging time for many businesses.”

Bruce Crawford, convener of Holyrood’s Finance Committee, took to Twitter to urge political rivals to support the Budget.

He said: “Opposition parties must get behind the SNP Gov #ScotBudget. Opposing it would mean voting down additional spending on our NHS, education, welfare and local services; causing serious disruption & risking unwanted Scottish Parliament election.”

However, Scottish Liberal Democrat leader Willie Rennie insisted there was no majority for the Budget in its current form.

He stated: “Scottish Liberal Democrats are not asking for the world. We want to deliver a progressive budget that delivers on education, mental health and local government funding.

“However, we have also been clear that independence would mean less money for public services. That’s why it needs to be taken off the table for the remainder of this parliament.

“If the SNP park the issue of independence for the rest of this Parliament then we could reach a comprehensive and progressive deal on the budget. As it stands, we will not be voting for the budget at stage one.”

Finance Secretary Derek Mackay said: “Our spending plans for 2019-20 provide a real-terms funding increase for Scotland’s essential public services, including additional funding of almost £730 million for our health and care services and more than £180 million to raise attainment in our schools.

“The budget also gives a vital boost to our economy through our £5 billion infrastructure investment programme, including a new £50 million Town Centre Fund to support the future of our high streets.”