Police officers have been told not to hand out fixed penalty notices in stalking and harassment cases after the teenager Shana Grice was fined for wasting police time before she was murdered.

The Independent Office of Police Conduct (IOPC) issued the recommendation to chief constables of all forces in England and Wales in the wake of the 19-year-old’s killing at the hands of her ex-boyfriend after he spent months stalking and harassing her.

Michael Lane murdered Grice at her home in Brighton on 25 August 2016. She had reported Lane to police five times in six months and had been fined for wasting officers’ time after she initially failed to disclose their relationship. The harassment case was closed before her pleas for help were properly investigated.

In its final report on how officers handled Grice’s complaints, the IOPC made a series of recommendations to Sussex police, advising them to properly train staff, improve risk assessments, communicate better and use systems correctly.

The College of Policing and National Police Chiefs’ Council have been told to get forces to make sure officers and staff have the skills to do their jobs properly when investigating crime.

An independent panel found former PC Trevor Godfrey committed misconduct in the way he handled a report of harassment by Grice. This represented the final disciplinary proceeding in relation to the IOPC investigation.

Sarah Green, the IOPC regional director, said: “We have been in regular contact with Sussex police during our investigation and since its conclusion, highlighting potential issues with how the force was handling allegations of stalking and harassment.

“HMICFRS [Her Majesty’s Inspectorate of Constabulary and Fire and Rescue Services] also conducted an in-depth assessment of the force’s performance on stalking and harassment and has raised concerns.

“It is vitally important that as part of our work, good practice is recognised and shared, while shortcomings, be it in policies, systems or training, are identified and improved.

“Sussex police responded positively to our informal recommendations but the HMICFRS report published in April shows there is still work to be done. The formalising of our recommendations is another step towards ensuring improvements are made.”

Grice and Lane had an on-off relationship, but when Grice finished it, Lane slashed the tyres of her car, assaulted her in the street and broke into her home. He also fitted a tracker to her car so he could monitor her movements.

Godfrey was tasked with investigating an allegation of common assault on 25 March 2016 after Grice claimed Lane had chased and made physical contact with her.

During an interview, Grice made a number of other allegations against Lane, including that he had sent her flowers unsolicited and made numerous attempts to contact her. Lane was arrested and told Godfrey the pair were in a relationship, and provided details of mobile phone messages to back up his story.

Grice admitted she was in a relationship with Lane, and in an 84-second phone call Godfrey told Grice she would be fined for wasting police time over the harassment allegations – a decision ratified by police bosses.

Lane, 27, was jailed for life with a minimum term of 25 years after he was convicted of Grice’s murder.