The conference at the Victoria & Albert museum was held in response to a survey by the nonprofit organisation Arts & Business which revealed that nearly 70 percent of arts organisations have experienced decreased levels of business investment since last year, and more than half of those said they suffered a drop exceeding 50 percent.
Spacey, whose Old Vic theatre relies heavily on the support of organisations including Morgan Stanley and asset management group CQS, said: "Having lived here for seven years I genuinely believe that the UK's pre-eminence in arts and culture constitutes one of the nation's most powerful natural resources.
"But many arts institutions are suffering, and without political will and both corporate and public support some will struggle to survive. It's time for us all to step up and ensure that our vibrant and diverse cultural life is protected."
Boris Johnson added: "Arts and culture are not a luxury, they are part of this city's DNA, its unique selling point. It is why people want to live and work here and seven out of ten tourists say it is a reason for their visit. At a time of recession it is more important than ever to invest in the arts."
Simon Robey, head of Morgan Stanley UK, warned that the business world forgets the arts “at its peril”, and encouraged greater interaction between arts organisations and the employees of the companies that sponsor them. Meanwhile, Boris Johnson proposed the introduction of US-style 'voluntary fees' system to sustain free museums through the tough economic times.