Standardised national assessments will not be implemented in a way which adds to teacher workload, Education Secretary John Swinney has said.

Mr Swinney's assurances over the national tests, due to be introduced next year for pupils in P1, P4, P7 and S3, come as teaching unions consider industrial action over existing "excessive assessment demands".

Read more: Pupils as young as five to sit school tests up to an hour long under controversial proposals

The Educational Institute of Scotland (EIS) is due to ballot its members, while the Scottish Secondary Teachers' Association (SSTA) has launched an indicative ballot over workload issues.

Plans for standardised tests were included in the National Improvement Framework, and are aimed at providing a clear measurement of the attainment gap across Scotland at various stages of the education system.

The Herald: John Swinney

Mr Swinney - who took up post as the Education Secretary just four days ago - told the BBC's Sunday Politics Scotland programme: "I am determined to take them (the tests) forward in a fashion which doesn't add to the workload of the teaching profession, but actually simplifies the workload of the teaching profession.

Read more: Teachers' leaders warning over "three hour tests" for primary pupils

"And that we do this in a fashion that we obtain meaningful comparisons about the performances in different areas."

When quizzed on who would mark the assessments, Mr Swinney suggested that not all of them will be externally marked.

He said: "It will be from age to age... give me some time to work out specific detail of how we will take that forward."

The Herald: The reintroduction of standardised national testing for Scottish schools has caused significant controversy with opponents arguing it will result in "teaching to the test"

On whether parents would have access to test results, Mr Swinney went on: "Of course that will be done in a transparent fashion but the key thing is it has to be done in a consistent fashion so that we can see where there are steps required to improve performance in different parts of the country."

During the interview, he acknowledged the scale of the challenge of tackling the attainment gap - which First Minister Nicola Sturgeon last week said was the "defining mission" of the government.

Read more: Secret Scottish government plans to shake-up schools system

"I go into this with my eyes wide open and there are some very significant challenges that have to be addressed."

He added: "I say to everybody: you have a willing pair of ears here who is prepared to listen to the issues and the challenges.

"I just ask people to give me a bit of space and time to try to address these issues and deliver on that top priority."

Scottish Conservative education spokeswoman Liz Smith said: "I have today written to the Cabinet Secretary to seek clarification about whether or not the new tests within primary schools will be externally marked. Parents and teachers want a straight answer about this as quickly as possible.

"We fully support the Scottish Government in its desire to replace existing tests with better quality formative and diagnostic testing in schools, but in a way that provides more meaningful results.

"These tests should be standardised at P4, P7 and S3 and they must come with the credibility of national marking criteria. This is exactly what happens further up the school when pupils sit SQA or other recognised qualifications."