Royal Mail shares close up 38%

Shares in Royal Mail have closed 37.9% up at 455p after a feverish first day of trading on the stock market.

Shares in the privatised postal service opened at 330p and jumped as high as 459p in early conditional dealings, which took place ahead of a formal launch on Tuesday.

The sharp rise has led to claims the 500-year-old company was undervalued, though the Government has defended its entry valuation as level with the rest of Europe.

Watch: PM says Royal Mail sell-off 'an excellent deal for taxpayers'

Prime Minister David Cameron hit back at criticism that Royal Mail was undersold by the government after shares soared 38% this morning at the start of conditional trading.

Speaking from Belfast he told ITV News the sell-off was an "excellent deal" for tax-payers.

Read: Union: Royal Mail has been 'flogged on the cheap'

More: Vince Cable says Price of Royal Mail shares 'tells us nothing'

Business Secretary Vince Cable dismissed claims that the government ripped off tax-payers by under pricing Royal Mail shares, and said today's inflated price was perfectly normal for a big flotation.

He said today's price tells us "absolutely nothing" about the offering and was merely "froth and speculation".

Read: Royal Mail workers protest outside Stock Exchange

Postal workers staged a protest outside the London Stock Exchange in the City this morning, as investors scrambled to buy shares in the 500-year-institution.

Bill Hayes, leader of the Communication Workers Union said the flotation was a "tragedy" and that the union would ballet members next week for strike action.

Appetite for Royal Mail shares have caused the website of one of the lead brokers involved in the float to crash. Hargreaves Lansdown's website experienced huge problems whilst phone lines were clogged, meaning some investors were unable to trade.

A spokesman for the firm apologised, saying the brokerage had seen "unprecedented demand."

Read: Trader describes busy morning on the stock market

Shares in Royal Mail soared by 36% in early trades, after the government set the price at 330p per share yesterday.

Traders are reporting a busy morning as clients, including those known as high-net-worth individuals (NHWI) who missed out having applied for more than £10K, scrambled to buy their share of the 500-year-old institution. Will Hedden, a sales trader with IG, explained:

Shares in Royal Mail, priced at 330p by the government this morning, soared to 448p shortly after markets opened.