Scotland met its annual climate change target for 2015, but transport has emerged as the biggest contributor to greenhouse gas emissions, according to new data.

Campaigners and politicians welcomed news that the 2015 statutory target was reached despite a slight rise in emissions compared with the previous year.

However opposition parties said more action is needed to tackle emissions from transport which "have barely changed".

Read more: Greenhouse gas emissions up but climate change target still met in 2015

Climate Change Secretary Roseanna Cunningham insisted the figures indicate Scotland is on course to meet its long-term goals, as she proposed increasing the 2050 target from an 80% reduction on 1990 baseline levels to 90%.

Emissions were measured at 45.5 million tonnes carbon dioxide equivalent in 2015, with the target for the year having been set at 46.928 million tonnes.

However, the total marked a small increase on revised figures for 2014, up 1.8% from 44.7 million tonnes carbon dioxide equivalent.

The Climate Change (Scotland) Act 2009 also contains an interim 2020 target to reduce emissions by at least 42% on baseline levels.

By 2015, a reduction of 41% had been achieved.

Read more: Greenhouse gas emissions up but climate change target still met in 2015

Speaking in Holyrood's chamber, Ms Cunningham said: "Scotland remains well on track to achieving its interim 2020 target.

"Our proposals to reduce emissions by at least 90% by 2050 clearly indicates to the people of Scotland that we remain resolutely committed to the fight against climate change."

Ms Cunningham told MSPs public consultation will begin soon on a proposed Climate Change Bill, while the Scottish Government's draft climate change plan will be published next year.

While cuts in emissions were welcomed, MSPs from all opposition parties raised concerns over transport.

Read more: Greenhouse gas emissions up but climate change target still met in 2015

Conservative MSP Maurice Golden said: "While overall the progress is encouraging, it would be incorrect to paint a picture of improvement across the board.

"Transport is now the single biggest source of carbon emissions."

Labour's Claudia Beamish said: "It is very concerning that transport is now the heaviest emitter... every year the Scottish Government reports the emissions inventory we have seen transport emissions barely change."

Scottish Liberal Democrat energy spokesman Liam McArthur said: "For years there has been insufficient action from SNP ministers to transform our transport system, boost active travel and attract people on to public transport.

Read more: Greenhouse gas emissions up but climate change target still met in 2015

"The Scottish Government's draft climate change plan lacks real ambition to reduce demand and encourage the shift towards low-carbon transport."

Pointing to plans to cut air tax, Green MSP Mark Ruskell said: "People throughout Scotland will want to know why the SNP is proposing unacceptable tax cuts for wealthy frequent flyers, but failing to make it cheaper to travel everyday by bus and train."

Jim Densham of the campaign group Stop Climate Chaos Scotland (SCCS) said: "Transport pollution has been stubbornly high for decades and we need significant action to catch up with other nations such as India and Norway which are planning to end the sale of fossil fuel cars by 2030."

Read more: Greenhouse gas emissions up but climate change target still met in 2015

Ms Cunningham said the Government aims to reduce transport emissions by a third by 2030 compared with 2014, and has invested over £1 billion each year in public and sustainable transport.

"It is a long-term project underpinned by technological innovation and our behaviour change approaches," she added.