CHAIRMAN Steve Gibson last night insisted that Middlesbrough are "serious bidders'' for Alan Smith - after Leeds accused Manchester United of trying to sign him on the cheap.

Crisis club Leeds revealed they had rejected two offers from Old Trafford for the 23-year-old striker.

Bids of £3.5m and £5.5m were rebuffed and a Leeds spokesman said: "The offers by Manchester United substantially undervalue Alan Smith's position as a top Premiership player.

"He's worth far more than Manchester United are prepared to pay for him and both offers were rejected immediately.''

Leeds rate Smith at nearer £10m and Liverpool are set to step up their interest.

Newcastle are also long-standing admirers and Gibson emphasised Boro's ambition by confirming that Smith and Leeds strike partner Mark Viduka remain prime targets.

The Boro chief said: "Alan Smith is going to have a lot of options. If Leeds get the right offer from Manchester United, I guess that's where he's going to go.

"But if it doesn't happen, we're there. The same applies to Mark Viduka - and others. We have a lot of options. There are players available right across Europe and we're trying to throw our net, pull in what we can, and have our choices.''

Tough-talking Gibson hinted at high-profile casualties as Boro look to overhaul their squad for next season. They have already released youngsters David Murphy, Sam Russell, Phil Gulliver, Craig Dove and Gary Smith.

Despite manager Steve McClaren leading Boro to Carling Cup final glory and their first major trophy, Gibson said: "We're not achieving what we should be with the players we have and we have been busy making some pretty tough decisions.

"Some players have been informed and others have yet to be informed. The squad we start with next season, both in terms of quality and quantity, will be substantially better than the one that finished the season.

"You can't pull the wool over people's eyes - we know our failings and we're working hard to put that right.

"We finished 11th with 48 points and we're disappointed. We're aiming for the top six and top ten should be the minimum.

"There's a bit of anger that the season has petered out again because everyone has worked hard and for some inexplicable reason we've turned off. We're professionals and that should not be allowed to happen.

"We've had a big inquest and a long discussion. The problem is that players haven't taken the chances they are paid to take.

"If we'd scored another six or seven goals, that would have probably taken us up two or three places and another ten goals would have probably put us in the top six.''

Gibson revealed there has been a 30 per cent increase in season ticket sales on the same period a year ago.

And he insisted the club are on target for a 32,000 sell-out next season, when they make their debut in major European competition in the UEFA Cup.

"In recent years we've probably had more support that we've deserved,'' admitted Gibson.

"But we're hopeful we're going to have full houses for the first time since Bryan Robson's days. The suggestions are we're on target.''

Birmingham, who yesterday signed former Boro target Emile Heskey from Liverpool in a deal worth up to £6.25m, believe they can lure Danny Mills.

Newcastle and Tottenham have also been linked with the right-back, who spent last season on loan with Boro and is understood to be available on a free from Leeds.

Bolo Zenden will link up with Holland for Euro 2004 with Boro hoping to entice him back to the Riverside next season.

The Chelsea winger, who like Mills was on a season-long loan, made a huge impact in the second half of the season and scored a penalty in Boro's Carling triumph over Bolton.

Gibson stressed: "We would very much like to keep Zenden. I think he's been our most consistent and best player since Christmas, and we're working desperately hard to keep him.''

Meanwhile, Brazilian midfielder Doriva yesterday signed a new one-year deal with Boro.