London - Ed Woodward admits the summer transfer window will be an "important opportunity" for Manchester United to bolster their squad with significant investment after a troubled season at Old Trafford.

United are languishing in eighth place in the Premier League as they struggle to secure a top four finish.

Both United manager Ole Gunnar Solskjaer and executive vice-chairperson Woodward have been under fire from frustrated fans, with some throwing flares and vandalising the outside of the latter's house recently.

Woodward points to the signing of Portugal playmaker Bruno Fernandes from Sporting Lisbon during the January transfer window as proof United can still attract quality players despite failing to win the Premier League since 2013.

But, while Solskjaer's team are still in the Europa League and FA Cup, Woodward conceded United's struggles so far have left them short of the pre-season targets.

"The signing of Bruno Fernandes and return of key players from injury will be a boost to Ole and the squad as we head into the second half of the season," Woodward said in introductory remarks made at a recent fans' forum.

"We remain in contention in the Europa League and the FA Cup, as well as for Champions League qualification, so there is still lots to play for.

"However, as a club and a board, we do recognise that we are not yet where we want to be.

"It is the overwhelming priority of everyone at the club to get us back to regularly challenging for Premier League and Champions League titles.

"Although progress may not always be smooth, everyone across the club is focused and committed on playing their part in helping achieve those aims."

The emergence of youngsters Mason Greenwood and Brandon Williams has offered hope for the future and Woodward wants to blend those promising talents with the more established stars.

With that in mind, he hopes the next transfer window will provide an opportunity to significantly improve United's squad.

"Our focus is on bringing in a combination of experience and the best young players with potential to develop further, fusing graduates from our academy with high-quality acquisitions," he said at the fans' forum.

"Our recruitment process focuses on analysis and selection of players over the course of a season, with a view to the following summer transfer window.

"As part of the rebuild we see this coming summer as an important opportunity.

"We had consistently taken the view that - because January is not an optimal time in terms of availability of players - we would only buy in January if players we had already targeted for the summer became available and we were pleased that this strategy played out with the signing of Bruno Fernandes.

"There has been no shortage of investment in players over the past few years, with over £200 million spent since Ole became manager."