The BII has refused to rise to calls from trade union GMB to strip Punch Taverns of its membership - but is set to take a close look at pubcos' codes of practice.
The GMB made the demand after releasing details about a dispute between Punch Taverns and tenant David Mountford of the Rising Sun in Middleton, Derbyshire.
The union claims Punch was misleading and threatening in its dealings with Mountford.
BII chief executive Neil Robertson was sent an 18 page letter from Mountford detailing various claims which the BII is still investigating.
He refused to be drawn on the specifics of the case but confirmed all potential code breaches are investigated.
He said: "Whilst we don't widely advertise the fact, we consistently get good outcomes for our members."
Robertson also said the BII was currently examining its Benchmarking and Accreditation Services Scheme (BIIBAS) which assesses pub companies' codes of practice.
He said: "We are currently in discussion with the pub companies regarding proposals to extend the scope and ambition of the scheme, however, at this time each code is examined and assessed for transparency and clarity. Therefore, some issues flagged up by Mr Mountford and GMB go beyond the remit of BIIBAS.
"They do, however, underline the importance of an industry mediation scheme, which, as we all know, is being introduced in response to the BEC inquiry report and will continue to drive up standards in business management.
On the GMB's calls to strip Punch of membership to the BII, Robertson said: "That's not really the point. This particular case is ongoing and, as I say, things do go wrong from time to time on both sides of a business arrangement.
"This issue is a matter for the BIIBAS board to investigate, look at the outcomes and take the action they deem appropriate."
Mountford took on the lease at the pub in 2007. He says he was promised £180,000 of investment in the pub but he claims Punch failed to deliver on that or carry out remedial safety work at the pub.
Martin Smith, GMB national organiser, described Mountford's deal as a 'pub tenancy from hell'.
"So compelling is his evidence that we plan to include it in GMB's wider submission to the OFT in our campaign to end the tie and the exploitation that goes with it," he said.
However Punch Taverns operations director, Kevin Georgel said many of the claims were "unsubstantiated".
"Whilst we strongly refute many of the unsubstantiated claims made by Mr Mountford, we are still in the process of exploring his complaint.
"The BII are acting as independent mediators in their capacity as accreditors of our Charter (BIIBAS) and we welcome their involvement in this matter.
"We regret that Mr Mountford has taken the decision to publicise his complaint at a time when we are actively engaged in addressing the issues in conjunction with the BII.
"We will continue to work positively with the BII to reach a conclusion."