Fennel pondweed has been discovered growing in Peasholm lake and has been getting caught in the rudders of the display ships, causing them to malfunction.

It is the first time the lake has suffered from this type of pondweed and it was only found in the last couple of weeks.

Action is being taken to clear the pondweed and it is hoped the weekend's Naval Warfare display will be staged as normal tomorrow at 3pm.

Roger Burnett, parks and countryside manager for Scarborough Council, said: "The main problem for us with fennel pondweed is that it can only be treated in its growing stage in March or April, so this course of action will not work at this time of year.

"The only option open to us is to remove it manually by hand."

He added that operatives have been clearing the pondweed but it was not clear enough to allow the displays to go ahead yesterday. They are continuing to clear even more.

Andrew Williams, leisure and community services officer for the council, added: "I would like to apologise for the inconvenience to any visitors and residents who had planned to watch the Naval Warfare but of course the other delights of Peasholm Park are still available for all to enjoy.

"In the long term, we will keep up the manual clearing of the pondweed to ensure that the displays can carry on throughout the summer season."