"Both [signs] were slashed, torn and stripped down ... It wasn't the sheep in behind there, I'll tell you that."
Mr Foss said the attack had saddened him.
"They weren't political signs, they were thank you signs - that's the bit that worries me.
"It's just a nice thing I always try to do.
"It's democracy, the people spoke, but these people are clearly angry."
In the lead-up to the General Election at the weekend, Mr Foss' election billboards were repeatedly vandalised.
In one instance, he woke to find 18 of his billboards defaced - some of them on Havelock Rd - in what he described as "a co-ordinated attack".
He said there had "absolutely" been more vandalism of political hoardings during this year's election than prior ones.
Asked if he had a message for the culprits, Mr Foss said: "The people that do this I don't think read the paper or participate in our community.
"They're scum, and a lot of other adjectives I won't use."