Royal Mail shares slid today after the letters and parcels firm highlighted fierce competition triggered by Amazon's launch of its own delivery network.

The company, which posted a fall in half-year profits, reduced its estimate for the annual rate of growth in the UK parcels market from a medium term target of 4% to as little as 1% over the next two years.

Royal Mail was the biggest faller in the FTSE 100 Index in a session when the top flight dipped 4.5 points to 6704.6 due to the impact of lower mining stocks.

Fears over the weaker outlook for iron ore prices in the next year led to falls of around 1% for market heavyweights Rio Tinto and BHP Billiton.

The pound strengthened against the US dollar at 1.57 after minutes of the most recent meeting of the Bank of England's monetary policy committee revealed a slightly more "hawkish" than expected tone

Members voted by 7-2 to keep rates on hold at 0.5% but among the majority "there was a material spread of views on the balance of risks to the outlook".

Days after economists at HSBC suggested a rate hike could come as late as 2016, the vote highlighted increasing concern about the potential for rising inflation. The pound was also up against the euro at 1.25.

A year on from its controversial flotation, Royal Mail's shares now stand at 434p, having slumped 7% or 34.65p today and by 30% since February.

Pre-tax profits fell to £218 million from £233 million a year earlier in the six months to September 28, although a number of one-off items distorted the performance and the results were still at the top end of City expectations.

Shares in inspection and product testing firm Intertek were down by a similar level after it issued a cautious trading update due to the impact of weaker commodity prices on the outlook for oil and gas related business.

Shares were 194p lower at 2459p.

Severn Trent was among the biggest risers in the top flight after a broker upgrade from HSBC ahead of results next week. Shares rose 41p to 2064p, while fellow water company United Utilites added 13p to 916p.

Outside the top flight, shares in pub groups fell sharply after MPs voted to reform the historic "beer tie" between tenants and pub companies.

Enterprise Inns, which has more than 5,000 pubs, slid 15% or 19.05p to 104.05p in the FTSE 250 Index after it said the Commons rebellion "threatens to have serious unintended consequences for publicans and the industry at large".

Rival firm Punch Taverns was down by 16.5p to 135p and Spirit Pub Company was off 7.75p to 100.25p, even though it has already agreed a takeover deal with Greene King.