By Shapi Shacinda LUSAKA, Jan 12 (Reuters) - Supporters of Zambia's main opposition party marched on Friday against IMF proposals for higher taxes as the government vowed to implement some of the suggestions in the next budget. Opposition Patriotic Front (PF) supporters were joined by some trade union leaders in the demonstrations which point to rising tension over higher taxes in Zambia, where most people remain extremely poor despite the country's vast copper wealth. Some 4,000 protesters, led by opposition politicians, presented a petition to Finance Minister Ng'andu Magande demanding that the government set aside International Monetary Fund (IMF) proposals for tax increases. They also demanded the reversal of the sale of 49 percent of shares in the Zambia National Commercial Bank (Zanaco) to Rabobank [RABN.UL] of the Netherlands. "Higher taxes are a recipe for poverty," read a banner carried by one protester who marched from Zanaco's Lusaka office to the Treasury. "Zanaco is our pride, don't sell it," another placard read. Populist PF leader Michael Sata, who narrowly lost presidential elections in September against President Levy Mwanawasa after a campaign which revolved largely around economic policy, addressed the crowd before the march. "We don't want the sale of Zanaco to proceed because this is our asset," Sata said in brief remarks. PF legislator Faustina Singyangwe presented a petition to Magande at the Treasury, saying the IMF was guiding Zambia in the wrong direction, particularly on the issue of value added taxes. The IMF has proposed adding value added taxes on food, mosquito nets, books, newspapers, magazines and transport to increase government revenues. Sinyangwe said Zambia should only introduce "a windfall tax" on higher profits reaped by the country's vast copper mines, which have enjoyed a period of high international copper prices. Magande, who was intermittently heckled by the protesters, said Zambia would implement some of the IMF proposals in the budget due at the end of January. "The IMF has made some good proposals like reducing corporate tax and pay as you earn (personal income tax). We will implement some of the proposals from the IMF just like we have done so on a number of suggestions from other institutions," Magande told Reuters. Magande told Reuters that the sale of 49 percent of Zanaco shares agreed two weeks ago -- part of a larger government drive to privatise some state assets under a programme agreed with the IMF -- was irreversible. "There is no reconsideration on the sale of Zanaco shares. If we go back on the agreement, then nobody can trust us in the future," Magade said, adding that the PF's Sata had himself supported some of the measures as a former minister in Mwanawasa's government. "The sale of Zanaco is one of the conditions we had to fulfil in order to continue enjoying the confidence of the donors. Mr Sata was in the government when this process started," Magande told the crowd.