The SNP will back the restoration of the 50p top income tax rate for those earning over £150,000 and support an increase in the Employment Allowance from £2,000 per business per year to £6,000 to help smaller firms take on and retain additional staff.

This allowance, which is currently set at £2,000 for tax year 2015-16, means employers receive relief from paying the first £2,000 of employers national insurance contributions (NICs). Under the SNP plan, the limit per business would be raised to £6,000 by 2019-20.

The manifesto states: 'This will provide a boost to employment growth by reducing the cost of creating and maintaining jobs. This proposal will particularly benefit smaller businesses with over 95% of the support going to smaller firms.'

The SNP also supports the creation of a Creative Content Fund for the games industry to encourage the formation of new studios and also back the retention of the video games tax relief, as well as industry calls for an increase in the Seed Enterprises Innovation Scheme (SEIS) investment limit and changes to the shortage occupation list to recognise specific skills needs in the sector.

It is also keen to retain the annual investment allowance (AIA) at £500,000 when it comes up for review at the end of 2015 before the current timeframe for the tax relief ends.

The manifesto also states: ‘We will also support a review of controlled foreign companies (CFC) exemptions and favour a rolling review of tax reliefs as part of an ongoing programme of simplification of the tax system.’

On tax avoidance and evasion, it is supporting the Scottish version of the General Anti Abuse Rule and would like to see an increase in staff resources at HMRC. It is also calling for a global fair tax summit to agree international measures to tackle tax abuses.

There will also be a boost for Scotland’s tourism and hospitality sectors with plans for a reduction in Air Passenger Duty, one of the devolved taxes.

It will also pledge to increase the minimum wage to £8.70 by 2020 and retain the triple lock on pensions.

SNP leader Nicola Sturgeon said: ‘We will also back fair proposals to raise extra revenue. It's right that those with the broadest shoulders pay a little bit more. That's why we will back the restoration of the 50p tax rate for the highest earners, a mansion tax, and a bankers' bonus tax.’

With potential to act as kingmakers on 8 May, the SNPs are still committed to independence but are playing this down in the run-up to the general election although they have restated their goal of having full control of taxation, including North Sea oil revenue.

With 59 seats up for grabs, the latest opinion polls point to a landslide in Scotland as Labour is set to lose the majority of its seats.

With the likely outcome of an election in the balance, the manifesto clearly states: ‘We will also vote for the following revenue raising measures - the reintroduction of the 50 pence top tax rate, a tax on bankers' bonuses, a bank levy, a mansion tax, a crackdown on tax avoidance, the abolition of 'non-dom' status and reversal of the married couple’s tax allowance.’

‘The SNP will always support independence - but this election is not about independence. It is about making Scotland stronger,’ said Sturgeon.

‘So we will use the influence of SNP votes at Westminster to ensure that the promises made during the referendum are delivered. We will demand that the proposals of the Smith Commission are delivered quickly and in full, and we will oppose any effort to undermine devolution.

‘We will seek agreement that the Scottish parliament should move to full financial responsibility. And as part of a phased transition,  we will prioritise early devolution of powers over employment policy, including the minimum wage, welfare, business taxes, national insurance and equality.’

Under the proposals in the Smith Commission on tax devolution issued after the referendum last year, 70% of Scottish taxes and 85% of welfare spending in Scotland remains under Westminster control.

The 56-page SNP manifesto is available here

General information is available at www.snp.org