Pompey could even have their next boss in place for Saturday's Fratton Park clash with Manchester United.

The club already have an ideal replacement for Hart at the club, after bringing in former Chelsea manager Grant as director of football last month.

Pompey intend to make a swift appointment however there was no indication on Tuesday night that Grant will inherit the job.

He has not given any public suggestion he wants to return to management with Pompey, and at the time of his appointment club chief executive Peter Storrie stressed the 54-year-old was coming in only to oversee football matters, rather than have a hands-on role with the first team.

Pompey may even turn to Darren Ferguson, with some bookmakers offering short odds on Tuesday night on the appointment of the out-of-work former Peterborough manager. Ferguson was sacked by the Championship club earlier this month but began the season with a burgeoning reputation.

That could offer the tantalising prospect of Ferguson taking on his father Sir Alex Ferguson's team at the weekend.

Coaches Paul Groves and Ian Woan have been put in temporary charge of the Portsmouth first team but that is a short-term measure.

Hart, the former Nottingham Forest and Barnsley boss, left Fratton Park with Portsmouth at the foot of the Premier League, after taking just seven points from 13 matches.

They were beaten 1-0 at Stoke on Sunday and are four points adrift of safety.

The club said Hart had turned down the role of technical director, with responsibility for players aged 18 to 21.

Portsmouth chief executive Peter Storrie said on the club website: "Paul has worked under very difficult circumstances with the financial restrictions the club has faced since he took over.

"However, the board feels that the team should have accrued more points to date and that we need a new man in charge to ensure Premier League survival.

"The board would like to thank Paul for his work not only in keeping the club in the Premier League last season but also for his time in charge of youth development.

"Paul is a man of great dignity and we hoped he would stay and help us develop younger players on the fringes of the first team.

We are genuinely sad to see him leave. Everyone at the club wishes him well for the future."

Hart was Portsmouth's director of youth operations until being handed the chance to take over from former manager Tony Adams in February this year, initially as caretaker boss.

After the team avoided relegation, Hart was named as Portsmouth's full-time manager in July, however they began this season with seven straight league defeats.

Portsmouth have since beaten Wolves and Wigan but have been unable to break away from the bottom of the league.

They have three consecutive home matches ahead, with United's visit on Saturday followed by a Carling Cup clash with Aston Villa on Tuesday and a league tussle with Burnley four days later.

Striker Danny Webber was signed by the club in the early weeks of the season, as they built a squad following several summer departures.

The former Sheffield United player admitted Hart's exit came as a shock.

He told Sky Sports News: "Paul was at training today and everything was as normal. I don't think any of the players saw this coming at all.

"I am sad to hear Paul has gone as I myself and all the lads have been impressed with the work he was doing and how he conducted himself.

"I don't think anyone would have any bad words to say about him."

Looking to the future, Webber said: "Whoever the new manager will be it is guaranteed they will have 100 per cent backing from the squad as everyone is determined to climb up the table."