A leading Conservative councillor criticised for receiving hospitality or gifts 893 times over six years, frequently from property developers seeking planning permission, has resigned after an internal investigation found he breached the authority’s code of conduct.

The Guardian revealed in February the extent of the hospitality lavished on Robert Davis, who was the deputy leader of Westminster city council and until last year the chair of its planning committee, overseeing billions of pounds’ worth of new property developments.

Sir Stephen Lamport, the independent person overseeing the investigation, said Davis’s judgement was found “wanting” and his “acceptance of gifts and hospitality from developers before or after a planning decision may … have placed him in a position in which people might seek to influence him in the performance of his duties.”

He said he had not seen any evidence that happened, but it still amounted to a prima facie breach of the code of conduct which will now be examined by the council’s standards committee.

The leader of the council, Nickie Aiken, welcomed his decision to quit saying: “The planning process must be and be seen to be impartial.”

Davis received tickets to West End shows and invitations to exclusive dinners in London’s finest restaurants as well as trips to the south of France, his official declarations revealed. One day in Mallorca he managed two lunches, the first at the home of Andrew Lloyd Webber and the second at the home of the Earl of Chichester.

He was entertained by and received gifts from property industry figures at least 150 times from the start of 2015 onwards – a rate of almost once a week. The Guardian established that he received gifts or hospitality from property firms involved in half of the planning applications his committee ruled on in 2016.

The review found that “by accepting the large scale of gifts and hospitality Cllr Davis has not promoted and supported high standards of conduct through leadership and by example”.

It said there was no evidence of any inappropriate conduct or illegality but the scale of the hospitality was “extraordinary”.

Lamport said Davis’ acceptance of such a volume of gifts and hospitality “lay open his reputation, and therefore that of the Council, to a perception – fairly or unfairly – that called into question his personal responsibility to promote high standards of conduct”.

Davis stood down from his role as deputy leader in March after an outcry at the scale of the hospitality, but denied any wrongdoing and stood again as a councillor in May’s local elections, retaining his seat.

In a statement on Wednesday he said that following an internal investigation led by a senior barrister appointed by the council, he was resigning with immediate effect, bringing to an end his 36 years as a councillor in the borough.

He said: “Earlier this year there was some press coverage concerning the hospitality I received during the course of my duties. To avoid this becoming an issue in this year’s elections, I agreed to refer myself to the monitoring officer and stand aside as deputy leader while an investigation was carried out. My approach to declarations has always been to be honest, open and transparent. I have nothing to hide.

“An inquiry has been completed by the council. They have confirmed that none of the declarations I made or hospitality I received influenced decisions I took as a councillor and that nothing I did was unlawful.

“However, they have concluded my actions nevertheless created a perception that was negative to the council. While I dispute this, I wish to draw a line under the matter. It is now time for me to move on to the next stage in my life and for the next generation of councillors to lead Westminster.”