The opposition should stop using the rail row to make "personal attacks", the transport minister has told MSPs.

Humza Yousaf apologised to passengers affected by delays and pledged to closely monitor progress in improving rail services until they return to "acceptable contractual standards".

There has been criticism of the reliability of ScotRail trains since Dutch firm Abellio took over the franchise.

Yousaf described current rail operations as not "a poor service" but he "fully understands the dissatisfaction of passengers and the inconvenience that is caused".

He told MSPs: "Let me firstly say to any passenger who has had a bad experience on our railways that I am sorry and that this government is committed to improving the service that you receive.

"Whilst no government or any minister can guarantee that major failures won't happen, I can advise that ScotRail has learned lessons to ensure that they are better prepared for contingencies and, importantly, communication with passengers when such incidents do take place.

"Indeed, today we have seen a much more responsive reaction by ScotRail which regrettably affected a much larger number of commuters in the Glasgow area."

ScotRail was forced to produce a performance improvement plan in September at the request of Transport Scotland after punctuality and reliability fell below standard.

The plan includes 250 individual actions and "work is well under way to deliver them".

Immediate improvements include £16m in infrastructure and £14m for improving the reliability of the fleet.

Revised procedures to focus on prompt departures from major stations have been put in place, while more carriages will be added to peak-time Borders services from mid-December.

More early morning services connecting north and central Scotland are also planned.

The minister added: "Let me be clear, this government expects the highest possible standards of our rail industry and to achieve that we have set some of the toughest targets of any franchise in the UK.

"It is the duty and responsibility of Abellio to fulfil their obligation under that contract.

"It is my job to hold them to account and I will personally be closely monitoring Abellio and their progress on the improvement plan until performance returns to acceptable contractual standards."

Yousaf also confirmed he will meet unions, political parties and others next week to set out options for a public sector bid to run the railways.

Such a bid could be ready for 2020 when a clause in the ten-year contract with Abellio would allow it to be broken.

Labour MSP Neil Bibby accused the minister of being on "the wrong side of Scotland's passengers".

He said: "The facts are the minister demanded an improvement plan and services have become worse. Staff morale is at rock bottom.

"His handling of the situation has seen him fall out with Abellio, Network Rail and transport unions."

He called on the minister to publish the full improvement plan, as did Liberal Democrat MSP Mike Rumbles.

Yousaf accused Mr Bibby of making "petty, pathetic personal attacks towards me" and of being "disingenuous" when claiming improvements have not been made.

Questioned on overcrowding, the minister acknowledged it is an issue and said extra carriages being introduced would ensure passengers had a better service.

Conservative MSP Murdo Fraser accused Yousaf of working on the public-sector bid "to try to win over the unions who have called for the minister's head".

He said: "We've heard a lot of promises from the minister today but what passengers want to know is when will they see improvements."

The minister said he "completely rejected" Fraser's comments the railways were a "shambles" and said ScotRail is performing 2% higher than the average for Britain and had 7% higher passenger satisfaction.

He said the SNP was bringing forward the public-sector bid as it was a manifesto pledge.

Green MSP John Finnie called for passengers to be automatically given compensation claim forms when ScotRail's performance is "low".

In response, Yousaf said ScotRail is reviewing its compensation procedures and this would be suggested to them.

Charlotte Twyning, director of policy, strategy and communications for Abellio UK, said: "Scotland's railways are undergoing an unprecedented period of investment and modernisation, addressing a legacy of underinvestment and ensuring that we have a railway of which Scotland can be proud.

"It is inevitable that managing an increasingly busy rail service while this important work is being undertaken will lead to some disruption, and it is our job to better engage with passengers to explain what is happening and listen to their frustrations."

She added: "It is our firm belief that collaboration will better serve passengers' interests and we will work hard with Humza Yousaf and Transport Scotland to build confidence in the railway and deliver improvements where we know they must be delivered."