The council has received the instruction from the Information Commissioner's Office (ICO), with Phillip Angell, Head of Freedom of Information (FOI) casework at the ICO, saying: "We’ve demanded it does better."
The ICO has issued an official 'enforcement notice' to the authority.
It comes after the council told the ICO it had a plan to clear its backlog by the end of March – but still had 143 unanswered requests at the end of April, the oldest of which dates back to April 2021.
The ICO said the council confirmed it had a "weak FOI request handling system", with individual service areas responsible for recording and collating their own FOI requests.
The enforcement notice requires the council to respond to all outstanding requests over 20 working days old, no later than six months from the date of the notice.
It is also required to devise and publish an action plan to mitigate any future delays to FOI requests, within 35 days from the date of the notice.
Mr Angell said: “People have a legal right to be able to ask their council about its actions and receive an answer promptly. In its poor handling of FOI requests Shropshire Council has been failing to be transparent and accountable. We’ve demanded it does better.”
He added: “Any public authority with poor Freedom of Information compliance levels may be subject to enforcement or practice recommendations as part of the ICO’s commitment to promoting openness, transparency and accountability.”
An enforcement notice is issued under s52 of FOIA, and requires a public authority to take specific steps to comply with part I of the Act. It is a formal notice issued to address system-wide or repeated breaches.
Failure to comply with the enforcement notice may lead to the council being found in contempt of court.
A spokesman for Shropshire Council said: "The Information Commissioner’s Office (ICO) has called on us to improve the way we deal with Freedom of Information (FOI) requests.
"We have already made improvements to our FOI processes and have been reducing the number of overdue FOI requests. However, we still have more work to do and we are working with the ICO to improve our compliance with the legislation."