Mendes and Davis found their opportunities limited after Spurs brought Edgar Davids and Jermaine Jenas to the club in the summer, while full-back Pamarot has only featured twice this season.

The fee for the three players is undisclosed but is understood to be around £7m (€10.1m).

All three players will be available for Saturday's crucial game at home to Everton - along with new strikers Benjani Mwaruwari and Emmanuel Olisadebe.

Manager Harry Redknapp has wasted little time in dipping into new Pompey co-owner Alexandre Gaydamak's funds and said: "I'm delighted to get three quality players I really needed and wanted.

"The side desperately needed improving and I always knew I had to put a team together that will get us out of trouble and back on track."

Davis, capped 11 times for England at under-21 level, said: "I've had my injury problems at Spurs over he last few months and it's been a bit of a nightmare training with the reserves and not getting a look-in with the first team.

"It's just great that the manager here came in for me. I could have moved in pre-season but decided to stay on and fight for my place. It didn't seem to make much impact with the manager at Tottenham."

The former Fulham midfielder cost Tottenham £3m (€4.3m) in July 2004 while Mendes, who won the Champions League with Porto the season before last, joined Spurs for £2m (€2.9m) last summer.

It will be a second spell at Pompey for Pamarot. The first was in September 1999 when the French full-back was on loan for a brief spell but when it came to joining a Premiership club permanently he was snapped up for £1m (€1.46m) by Tottenham two seasons ago.

Redknapp insists there may still be more players to come in before the end of the transfer window.

Gaydamak has promised around £10m (€14.6m) to spend on new players and the manager said: "I'm still looking.

"I'm sure other clubs were interested in the players we've signed today. I've never signed three from one club before all at once but these are top Premiership players and will be a massive asset to us."

Mendes, 26, said: "I don't regret moving to England from Portugal. I had a good start in my career at Tottenham but obviously the last few months have not been very happy for me.

"It's a big challenge we are facing trying to lift Portsmouth up the table.

"But mainly I have made this move for my own happiness. I'm very proud that the manager here was so keen to sign me and I am going to do my best to help get the team out of trouble."

Redknapp has also been linked with Norwich goalkeeper Robert Green. However, Redknapp's own keeper, Jamie Ashdown, is making a good recovery from back trouble and the manager said: "Green belongs to Norwich and I have not even spoken to their manager Nigel Worthington about it.

"There is still a possibility Jamie could be ready for this weekend or at least the weekend after. We'll wait and see how it goes."