The City of London Corporation and St Paul's Cathedral will seek injunctions to evict the anti-capitalist protest camp from the grounds of the historic building, as clergy prepared to celebrate its reopening with a lunchtime service.

A statement from St Paul's, issued moments before it opened its doors to the public after a week's closure on health and safety grounds, said legal action against the Occupy the London Stock Exchange camp had "regrettably become necessary".

"The Chapter has previously asked the encampment to leave the cathedral precinct in peace. This has not yet happened and so, following the advice of our lawyers, legal action has regrettably become necessary. The Chapter only takes this step with the greatest reluctance and remains committed to a peaceful solution.

"At each step of the legal process the Chapter will continue to entreat the protesters to agree to a peaceful solution and, if an injunction is granted, will then be able to discuss with the protesters how to reach this solution."

"Theirs is a message that the Chapter has both heard and shares and looks forward to engaging with the protesters to identify how the message may continue to be debated at St Paul's and acted upon."

The cathedral is still reeling from the departure of its canon chancellor Giles Fraser, who stepped down because he could not sanction the cathedral using force to remove protesters.

Earlier on Friday, the City of London's planning and transportation committee voted overwhelmingly in favour of "the commencement of proceedings to remove the encampment" because it constituted an "unreasonable user of the highway". It could serve notice as early as Monday.

A corporation source told the Guardian: "There is an expectation that [the legal process to remove the camp] will take a lot of time."

A report presented to committee members claimed there were 248 tents in the grounds of St Paul's. The document looked at the right to peaceful protest with a reasonable user of the highway, in this case the area around the cathedral.

"If this [Occupy London] were not a camped protest it would constitute a reasonable user of the highway. The City of London Corporation is not seeking to prevent protest but to limit the exact nature and form of protest it has chosen. A 24-hour non-camped protest would be permissible in this location."

The corporation's principal objection lies with the tents as they do not have planning permission to be there, said the source.

Committee members also learned of the protest's impact on pedestrian activity around the cathedral.

The report said there were 2,610 pedestrians around St Paul's during a one-hour period on one day in February 2011. At the same time of day, but on 25 October, the 11th day of the protest, there were 1,750 pedestrians. It also highlighted harm to the visual impact of the cathedral.

The report claimed that people were urinating in cathedral grounds and placing excrement in the bins.